The concept of urban morphogenesis has been applied most often by geographers to specific building types, stressing the origins of the city's physical form (Vance 1977). In this sense the city has been viewed as a collection of morphological areas, based upon physical components of urban spatial structure (Herbert 1972). Except for an article on the morphogenesis of Detroit's black ghetto (Deskins 1981), the concept has not been studied explicitly in terms of the shaping of social districts in the city.

This paper advances the notion of urban community morphogenesis to analyze the evolving human and physical features of an ethnic district. It extends the traditional morphogenetic concept to include the emergence of form in a social area, focusing upon the processes through which emergent social groups adapt the urban environment to new uses. Specific building types inevitably are involved in the geographic processes of community formation, but the central concern here is the structuring of an inner-city neighborhood and the creation of its distinctive ethnic identity. The morphogenesis of this specialized urban community represents an adaptation of the city's spatial structure that can be examined on a small scale to indicate the evolution of both ethnic enclaves and ethnic identities.

Ethnic identification is commonly conceptualized as a simple matter of allegiance to primordial religious, naational-origin, or racial groups. This paper argues that upon close inspection ethnicity is not such a static, clearcut, or homogeneous phenomenon; instead, ethnicity represents an intricate and evolving set of group identities. Ethnic identification is variable in time and space and constitutes a process of human adaptation to specific ennvironments.

Observers often do not fully appreciate the importance of the spatial and temporal contexts within which ethnic identities emerge. Immigrants perceive themselves both in terms of their background and the nature of their contacts with the receiving society; this interactive process fosters the acquisition of new group identities. A study of West Indians. in London, for example, found that an ethnic identity "based upon blackness [was] emerging," despite prior cultural and national differences between backs (Midgett 1975). On the other hand, outward racial similarities may disguise internal ethnic differences, as in the case of West Indians in New York City, who are often lumped together with North American Blacks (Conway and Bigby 1983).

Immigrant groups manifest varying degrees of both ethnic syncretism and separation. They may form a new ethnic identity as part of a wider minority group but still maintain a more specific sense of regional origin--in a sense, subcultures are formed within wider subcultures. An example of this is that Vietnamese in the United States come to see themselves also as Asian-Americans, Haitians as blacks, and Salvadorans as Hispanics. The degree of subcultural cohesion and fragmentation varies, deepending upon factors specific to each minority group. Examination of the historical geography of immigrant settlement, as reflected in urban community morphogeenesis, clarifies the evolution of different ethnic identities.

Hispanic communities in American cities show the complexities of the countervailing forces that affect subbcultural formation and dissolution. Certain common culltural traits, most notably the Spanish language itself, provide a unifying focus in American society, while national and regional differences provide the basis for differentiation, as it does in San Francisco's heterogeneous Hispanic community, made up of diverse Latin American nationalities. About 39 percent of the city's total Latino population is of Mexican origin, 6 percent is from Puerto Rico, 2 percent is from Cuba, and 53 percent is what the 1980 U.S. Census categorizes as "Other Spanish Origin." These "others"--or Los Otros, to use the Spanish--come mainly from Central American countries. Among major American cities, San Fransisco probably has the highest proportion of Central American Hispanics.

The city's fastest-growing Central American groups, which together outnumber Hispanics of Mexican origin, are from strife-torn Nicaragua and El Salvador. Scholars have overlooked the history, nature, and extent of Central [end p. 45] American migration to both San Francisco and the United States generally; only the news media, because of the contemporary upheavals in Central America, have paid even cursory attention to this large-scale migration. Yet Central Americans and other Latins have migrated to San Francisco in significant waves ever since the gold rush, setting the preconditions for the more recent influx (Godfrey 1984).

This Central American migration to San Francisco must be understood in terms of both the city's traditional role as a major port of entry on the West Coast and its commercial ties with Latin America. A historical geography of ethnic settlement in the city, considering both external and internal variables, helps to explain both the nature of local Latino group identities and the morphogenesis of San Fransisco's contemporary Hispanic neighhborhood or barrio.

EXTERNAL CONNECTIONS AND LATIN AMERICAN IMMIGRATION
The mercantile model of settlement can be used to explain the large Central American component of San Francisco's Hispanic population. This model holds that long-distance trading connections create a wholesale commodity entrepot, which then becomes a social entrepot for migrants (Vance 1977, 1982). San Francisco's role as a primary destination for Central American immigrants to the United States fits well into this scheme, given the city's historic position as a mercantile center of commercial interests along the Pacific Coast.

San Francisco has maintained transportation ties with Central America since the mid-ninteenth century. During the California gold rush, the Pacific Mail Steamer and other vessels ran regularly between the East Coast and San Francisco via overland connections on the Central American isthmus, mainly in Panama and Nicaragua. Coffee became an important cash crop in Central Amerrica during this period and a brisk export trade developed with the West Coast, with San Francisco as the chief processing center. Companies based in the city --Folger's, Hills Brothers, and MJB--fostered contacts with Central America's coffee-producing areas; once these links were established, social networks led to incipient migratory movements, both to and fro, limited at first to members of the coffee oligarchy and other elite families.

Immigration from Central America increased during the early twentieth century. Many Salvadorans, Nicaraguans, and other Central Americans were recruited to work on construction of the Panama Canal; afterwards, much of this mobile labor force joined shipping lines operating in the Canal, leading many Central Americans to come to San Francisco, which remained the principal port on the Pacific Coast until after World War II. Simmilarly many Mexicans, fleeing the dislocation of the revolution or attracted by the prospects of jobs, came to San Francisco during the prosperous, labor-scarce 1920s. In addition, many Puerto Ricans and other Spanish-speakers entered San Francisco during the 1920s from Hawaii, where they had worked in plantation agriculture (Leyland 1980).

Census figures reflected these pre-depression migratory waves. After decades of relative stability, the number of Mexican-born immigrants in San Francisco more than quadrupled between 1910 and 1930, reaching 7,900 or 5.1 percent of the total foreign-born population. During the 1920s, immigrants born in Central and South America more than tripled to more than 3,200 or 2 percent of the total foreign-born population (U.S. Census, various years).

Many Latin American males worked as laborers near the San Francisco waterfront, especially south of Market Street (Figure 1). The coffee companies were located there, as were canneries, agricultural refineries, and inndustrial plants needing manual labor. Also situated nearby were the United Fruit Company Docks, where a banana boat arrived weekly from Central America. The United Fruit Company operated three freight and passsenger steamships between San Francisco and the west coast of Central America, where banana plantations were moved in the late 1920s and 1930s to escape a banana plague on the Caribbean side (West and Augelli 1982).

SAN FRANCISCO'S CHANGING ETHNICITY
After a decline during the depression era of the 1930s, San Francisco's Mexican-born population increased only moderately to 5,600 (4.6 percent of the total number of foreign-born) during the 1940s. Mexican immigrants tended to be absorbed in the bracero agricultural labor program, started in 1942, and settled more in the East and South San Francisco Bay regions, where agriculture still flourished. Meanwhile, the Central and South American-born population more than doubled to 6,855 (5.6 percent), so that by 1950 it already outnumbered the Mexican-born. The labor scarcities of World War II stimulated this increase in the Central American-born population of San Francisco: shipyards and other wartime industries in the Bay Area recruited not only Blacks from the U.S. South, but also significant numbers of Central Americans from El Salvador and Nicaragua. Although the proportion of Mexican immigrants declined in the 1930s and 1940s, many Chicanos, children of migrant farm workers from the Southwest, did move to San Francisco during and shortly after the war. These second generation Mexican-Americans tended to predominate in the affairs of the Hispanic community.

Central American immigration to San Francisco increased steadily during the postwar period, as family ties drew new migrants to the city. By 1970, the city's Hispanic population of Central and South American origin reached 27,000, mainly from El Salvador and Nicaragua. In the same year, the total number claiming Mexican origin was just 18,500 (U.S. Census, various years).

Until the late 1970s, the migratory process followed [end p. 46]

the familiar socio-economic "push-pull" pattern: lack of opportunity for advancement at home led to a widespread movement to the United States. San Francisco was an attractive destination for aspiring Central American immigrants of urban working-class and professional backgrounds (González 1976). In the late 1970s, however, Central American immigration changed in nature and accelerated in volume. As the region's political situation became increasingly oppressive and chaotic, many were forced to seek political refuge abroad. Nicaraguan opponents of the Somoza regime fled to the United States before the strong man was overthrown in 1979. After this, opponents of the Sandinista regime came to San Francisco, bringing contra political activities with them. The internal crisis in EI Salvador, which flared up in the late 1970s, brought many Salvadorans to San Francisco. Significant numbers of Guatemalans also began to appear. Community activists estimate that since 1977 the number of Central Americans in San Francisco has douubled or even tripled, but the fact that many came as undocumented migrants makes this estimate impossible to confirm.

San Francisco's historic connections with Latin America explain its popularity as a destination for Central American migrants. The Pacific maritime routes encouraged labor flows before and during World War II, which in turn promoted larger-scale Central American immigration to the city, long before the contemporary flight from political oppression became a significant facctor. This structural explanation accounts for the Hispanic population being predominantly non-Mexican in San Francisco, as well as in satellite suburban communities in nearby San Mateo and Marin counties. On the other hand, the East and South Bay areas, which were more agricultural, drew Hispanics of predominantly Mexican origin as field laborers (U.S. Census, various years). [end p. 47]

SETTLEMENT INITIATION IN THE MISSION DISTRICT
San Francisco's Mission District has been the home for successive groups of migrants. Contrary to widespread local opinion, the District has not always been predominantly Hispanic, despite its historic Spanish and Mexican origins. The morphogenesis of the contemporary barrio reflects the adaptive processes by which emergent social groups made use of the existing urban built ennvironment, maintaining and modifying it according to changing community needs. The area's previous settlement history, however, affected this recent ethnic evolution.

The Mission San Francisco de Asis, popularly known as Mission Dolores, was founded in 1776. During the early 1830s, Mexico secularized the California mission lands, turning them over to Mexican soldiers and settlers, the Californios. Today, the names of Mission District streets-such as Guerrero and Valencia-still recall the local Mexican settler families; but the Hispanic origins were all but obliterated as American settlers poured into the area during the late nineteenth century. Mission Dolores was the principal landmark as the area began to be urbanized, however, and the area took on the name Mission District (Figure 2).

As San Francisco expanded from Yerba Buena Cove after the gold rush, settlers squatted on the former ranchos in the Mission District; by the 1860s, many of the land claims of these squatters were legitimized over those of Mexican land grant holders. A street grid was platted in the "Mission Addition" in the 1860s and 1870s, opening the way for residential growth. As part of the developing urban fringe, the Mission initially attracted recreational facilities and resorts, featuring theaters, race tracks, formal gardens, and zoos. Gradually the District was transformed from countryside to cityscape, as larger holdings were subdivided for housing development. The population of the city's 11th Ward, in which the Mission constituted the main settled area, grew from only about 3,000 in 1860 to some 23,000 by 1870 (U.S. Census, various years).

The Mission District became an attractive residential area during the late nineteenth century, noted for its good weather, convenient transportation facilities, and quasi-suburban atmosphere. Although the District never took on the ostentatious air of Nob Hill, some wealthy San Franciscans settled in the Mission and built mansions during this period, particularly along Howard Street (now South Van Ness Avenue). By the turn of the century, however, the District became more densely populated and took on a more working-class air. An enduring landuse pattern emerged. Industrial activity--including foundries, breweries, tanneries, warehouses, and factories producing bottles, furniture, and mattresses--became concentrated in the northeast comer of the Mission, as a functional extension of the South of Market District toward the Bay (Figure 1). The rest of the Mission became a heterogeneous mixture of single-family houses and multi-family buildings, combining residential and commercial functions (stores and services on the ground floors) along the major transportation arteries of Mission, Valencia, 16th, and 24th streets.

The San Francisco earthquake and fire of 1906 spared most of the Mission District. The conflagration was stopped in front of Mission Dolores, so it destroyed only the northern quarter of the District. Although Mission Street initially benefitted from increased retail activity while downtown was rebuilt, the 1906 earthquake ultiimately ended the District's pretensions of affluence. The city's housing shortage encouraged the development of increased densities in the Mission. The larger old houses of the District were steadily subdivided and the remaining vacant lots were developed, often with higher-density flats and apartments built to house refugees from the ravaged areas. Many displaced Italians from North Beach moved into the District, as did Irish, Germans, and Scanndinavians from the South of Market area. These newcomers lowered the social standing of the District, making it a more strictly working-class area. By 1910 the population of the Mission District exceeded 50,000, of which about a third was foreign born (U.S. Census 1910).

Foreign immigration slowed during World War II, and [end p. 48]

then again during the late 1920s . The Mission District became chiefly an area of secondary ethnic settlement, a place to establish familial roots after immigrants had already spent a few years in the city. The Mission District was attractive to blue-collar workers because it was centrally located and convenient to public transportation routes leading to the city's blue-collar employment cennters south of Market Street and along the waterfront.

The Mission District remained a stable working-class neighborhood during the inter-war period, inhabited for the most part by increasingly acculturated European ethhnic groups, whose children intermingled in school and often intermarried. The development of a characteristic local accent, sometimes compared to Brooklynese, reflected the community stability. But gradually the Misssion District was becoming a lower-income and increasingly dilapidated residential area. By the late 1930s the North Mission was among the city's lowest in socio-economic status, just a step up from the South of Market zone. Conditions in the District core were already well below par: over a third of all the housing units in the eight city blocks surrounding Alabama Street, beetween 20th and 24th streets, were either in need of "major repairs or unfit for use" (W.P.A. 1940).

By the time of World War II, the Mission District had experienced a steady downward filtration of the housing stock and was ready for a process of ethnic succession. The percentage of the Mission's population born abroad gradually declined from more than 33 percent in 1910 to under 19 percent in 1950, consistently under the city-wide average. With the influx of Latin American immigrants after 1950, however, the proportion of foreign-born in the District rose to new heights: 22.0 percent in 1960, 33.5 percent in 1970, and 37.8 percent in 1980 (U.S. Census, various years). [end p. 49] MORPHOLOGICAL ADAPTATION: THE MAKING OF A BARRIO
During the late 1800s, San Francisco's Latin American population had clustered in North Beach. A Spanish-language Catholic Church, Our Lady of Guadalupe, was founded there in 1875. But the Hispanic community of North Beach was unable to expand greatly during the twentieth century. First, Italian migrants competed for space during the early part of the century, and then the development of the bohemian nightclub and restaurant complex after World War II raised rents and forced the growing Hispanic population to move into other parts of the city.

Before World War II, increasing numbers of recent Hispanic immigrants already had begun gathering in the South of Market area, a traditional low-income point of entry for new European-stock arrivals to the city. Many Latin American males worked on or near the docks, close to the United Fruit Company Docks, the coffee companies, canneries, warehouses, and light industry. Like other immigrant groups before them--the Irish, Gerrmans, Scandinavians--Latin Americans began during the inter-war period to move southwestward from the South of Market area, following the street grid into the Mission District. Flats in the North Mission area were among the cheapest in San Francisco, rents being more than a third under the city average (W.P.A. 1940; U.S. Census 1940). By 1940 the first Spanish-language religious congregation appeared in the North Mission.

The Mission District's small Hispanic colony began to grow steadily during the late 1940s, as the older groups abandoned the area and rents remained low. Sixteenth Street became the first thoroughfare in the District with a significant Latin American cluster, attracting Hispanic restaurants, bakeries, and specialty shops in the early postwar years (Polk's S. F. Directory, various years). Census tract data for Hispanics in 1950 (the first year available) shows the highest concentration still in the South of Market and North Mission districts, after which the Latin American population continued its southward migration into the Mission Core (see Figure 3). The perception of the Mission District as a poverty area solidified after World War II. Latin American men worked in small manufacturing shops, warehouses, and other blue-collar occupations located close by in the North Mission, South of Market, and waterfront areas; many Spanish-speaking women were employed at the Ligget and Myers cigarette packing plant at 4th and Brannnan streets. Although the Mission District already was solidly working class, the influx of new immigrants made it decline further in social status. Increasingly residents of European stock moved out, spurring an ethnic successsion from European to Latin American.

The 1950s were the real period of "Hispanic invasion," as the Mission District's Spanish-surnamed population rose from 11 percent in 1950 to 23 percent in 1960. By 1970, 45 percent of the District's population was Hispanic (Table 1). The area in Mission Core east of South Van Ness Avenue reached an average of over 60 percent Hispanic in 1980, probably a conservative figure because of the many undocumented residents. Residential listings in the city directories show that along Alabama Street, between 21st and 23rd streets in the heart of the barrio, the proportion of heads of household with Spanish surnames rose from 29 percent in 1953, to 55 percent in 1963, to 72 percent in 1973, and to 74 percent in 1982 (Polk's S.F. Directory, various years). Presumably these percentages, based upon heads of household, under-represent the total Hispanic population, given its larger than average household size.

Residents often mention the Mission's climate--warmer than most of San Francisco--as an attraction for Latin American migrants. But socio-economic factors appear to be more important. Spanish is widely spoken in the District and the existing Hispanic population maintains family and social contacts in Latin America, perpetuating the migratory patterns; in addition, the Mission's housing remains cheap by San Francisco standards (González 1976; Leyland 1980). New immigrants tend to settle initially with relatives, which can entail considerable cramping of living quarters in the densely populated Mission. In addition to family, a variety of support services exist for new immigrants: resettlement programs, community and church groups, language and vocational training schools. Still, the lack of employment among Hispanic immigrants remains a major problem in the Mission District. [end p. 50] After some years in the Mission, usually working in the service sector (especially in restaurants and janitorial services) and construction trades, the more successful immigrants often move to outlying parts of the city or to suburban areas, such as the Outer Mission, South San Francisco, or Daly City, which have experienced a notable influx of Hispanics in recent years. Movement out of the Mission is a sign of upward social mobility and acculturation. This continual turnover of the immigrant population maintains the Mission District's ethnic enclave.

Twenty-forth Street in the Mission Core has come to serve as the banner street of the barrio. St. Peter's Catholic Church, located on 24th and Florida streets, now has an overwhelmingly Spanish-speaking congregation. Local businesses also reflect the population of the surrounding barrio streets. As opposed to the higher-rent properties on Mission Street, where national chain stores and larger commercial operations predominate, the businesses on 24th Street are smaller, more often family run, and highly ethnic in character. In 1953, eleven businesses indicated Spanish surnames or products on lower 24th Street, constituting roughly seven percent of the store-fronts along the thirteen-block thoroughfare. There were thirty-two such Hispanic-identified storefronts by 1963 (21 percent of the total), sixty in 1973 (40 percent), and eighty-two in 1982 (54 percent). The most common Hispanic businesses have been restaurants, grocery stores, and specialty shops. These ethnic businesses have represented a wide variety of nationalities, but the most common have been Mexican, with a smaller number of Salvadoran and Nicaraguan, and a scattering from South American and Caribbean countries (Polk's S.F. Directory, various years).

HISPANIC DIFFERENTIATION AND COHESION
Central Americans were not specified as separate Hispanic-origin groups in the 1980 U.S. Census, thereby falling under the general category of "Other Spanish Origins." In San Francisco, Central Americans predominate among Los otros--origins other than Mexican, Puerto Rican, and Cuban, the Hispanic nationalities included in the census count. Although the Latin American national groups are not strictly segregated within the Mission District, there are areas of concentration. Mexican-Americans cluster most in the heart of the barrio, while Central Americans predominate in the western and northern parts of the Mission District, and in the Outer Mission District (Figure 4).

The spatial differentiation reflects a degree of social class differentiation by nationality within San Francisco's Hispanic community. Central Americans inhabit the more affluent and less Hispanic areas, while Mexican-Americans are concentrated in the lower-income Mission Core. These spatial patterns appear to confirm the widespread local view that Central Americans are generally more upwardly mobile in the United States, simply because they are longer-distance migrants. The farther away the sending areas, the more selective is the immigration in terms of the social class of the participants (González 1976, 35-37).

Participation in local politics by Hispanics has been ineffective partly because of the number of undocumented residents who are ineligible to vote and partly because of the diverse Latin American origins of the population. Also, many recent immigrants have been preoccupied by political struggles in their homelands; and changes in regimes in Central America have conntributed to the development of rival factions among emigrés in the city. Nonetheless, the internal differentiation of San Francisco's Latin American population has not precluded the development of a wider pan-Hispanic cohesion. The diverse nationalities are beginning to forge a larger Hispanic identity.

This heightened ethnic solidarity is highly visible. At least 50 major public murals have been painted in the area since the early 1970s, inspired by Latin American muralists and emphasizing the Hispanic presence in the barrio. The Cinco de Mayo parade has been an anual event for the Latino community of the Mission since 1965. Although the parade celebrates a Mexican holiday, the defeat of the French at the Battle of Puebla in 1862, Central American groups have entered floats and are highly visible celebrants. A Latin American carnival equivalent to Mardi Gras, emphasizing the common cultural roots of diverse groups, has taken place in the Mission District since 1980. In recent years, the most heavily Hispanic part of the Mission, the area around lower 24th Street (east of Mission Street), has sponsored a Latino street fair.

The emergence of a Hispanic ethnic identity among Latin American immigrants in the Mission District is in part a generational process. The Mission District has a high proportion of youth, comprising about a third of the population. Crowded living quarters in the Mission, a widely acknowledged lack of recreational facilities, and high unemployment make the street a logical place for young people. So the Latino presence has become idenntified in the public eye with the activities of young people, especially low-riders and gangs, who attract the attention of the news media and the ire of the police. There are at least seven Hispanic youth gangs in the Mission Disstrict, organized more by neighborhood turf areas than by national origin (Navarro 1983). These street gangs contribute to the neighborhood's forbidding reputation, which serves in part as a defense against invasion by non-Hispanics.

Latino efforts to defend the territorial autonomy of the Mission date from the 1950s, when public housing projects were proposed for the District. A few were built, but local residents were aware that displacement had followed such projects elsewhere in the city, so they resisted massive redevelopment in the Mission. During the 1960s, the construction of the Bay Area Rapid Transit [end p. 51]

(BART) subway line up Mission Street raised controversies over building densities and height limits, ultiimately prompting the implementation of controls on development near the BART subway stations at 16th and 24th streets. Nonetheless, fears of displacement rose as average monthly rents in the Mission District more than doubled from $105 in 1970 to $223 in 1980; this rate of increase exceeded that of the city-wide average, which climbed from $135 to $266 during the 1970s (U. S. Census 1970, 1980).

The edges of the Mission District have been "gentrified" by youngish, affluent Anglos, who have started new businesses and restored many older residences in one of San Francisco's principal Victorian neighborhoods. The erosion of the barrio by gentrification has been most notable in the West Mission, where the number of Latinos has declined in both absolute and relative terms; undoubtedly this has been a factor in the widely publicized conflict of recent years between Hispanic youths and homosexuals (Bronstein 1980). In the Mission District Core, however, the number and percentage of Hispanics increased during the 1970s (Table 1).

In spite of gentrification and other encroachments, San Francisco's Hispanic population has become increasingly concentrated in the Mission District. Whereas less than 23 percent of the Spanish-surnamed population of the city resided in the Mission District in 1970, the percentage increased to over 27 percent by 1980, even though the city's total Hispanic population was reported by the U. S. Census to have dropped 17 percent (U. S. Census, various years). This increased city-wide Hispanification of the ethnic core and the erosion of the flanks within the Mission, has increased feelings of general Latino cohesion in the District (El Tecolote 1978; La Verdad Hispaña 1980).

Despite prior differences in Latin American nationality, there are shared social and cultural traits, especially the Spanish language and extended family patterns. Competition with non-Latin groups over such scarce resources as jobs, housing, and inner-city territory increases pannHispanic solidarity. The presence of an entrenched Hispanic minority in the barrio does not entirely prevent but it does check neighborhood gentrification and displaceement.

CONCLUSIONS: URBAN SPATIAL STRUCTURE AND THE ETHNIC COMMUNITY
The experience of Latin Americans in the Mission District shows how the specific historical-geographical facctors involved in ethnic settlement influence the process of community morphogenesis. The primary initial impetus for immigration came from external economic relationships, as in the mercantile model of settlement: the historic trade routes of the Pacific encouraged the development of San Francisco's large Central American population, long before contemporary politics became a cause of refugee resettlement. Within the city, Hispanic settlement reflected long-term processes of neighborhood succession. The first area to experience a significant Latin American influx was the North Mission, where immiigrants found low rents, housing vacancies, and proximity to blue-collar occupations. The ethnic community iniitially formed largely in response to functional socionomic characteristics, on a local as well as long-distance level.

Once established, however, the ethnic community became self-perpetuating, influencing as well as reacting to the urban environment. Despite a steady rise in both rents and house prices since World War II, in absolute and relative terms, the Hispanic barrio still has steadily solidified in the Mission Core. Although ethnic intensification did slow down in the 1970s, probably in part reflecting rising rents, erosion of Hispanic territory has been limited thus far mainly to the western flank. This suggests that Hispanic social networks and cultural traaditions, as well as economic status, have become strong enough to influence the evolution of the area's spatial structure.

Minority communities form in specific places in the city: barrios and other specialized districts are in a sense incubators of ethnic subcultures. This relationship between urban culture and spatial structure is reflected in the morphogenesis of the Hispanic community of the Mission District. The barrio is a place of subcultural formation, where a cohesive ethnic identity is forged out of diverse regional and national origins. As has been the case with other immigrant groups in the United States, the emergence of the Hispanic ethnic identity in San Francisco's Mission District has been closely related to the morphogenesis of the Hispanic ethnic enclave in the inner city.

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