The role, symbolic and substantive, of the Chicana/o populace in California has had a major influence on the politics and culture of the Southwest. The evolution of the historic East Los Angeles (East L.A.) barrio, the largest concentration of Chicanas/os and Mexicanas/os outside of Mexico City, was and is an essential reality of a culture of difference in an urban context that magnifies virtually all facets of the urban crisis. Other cities in the Southwest, all of which also have substantial and expanding Chicano/Mexicano barrios, pale in comparison to the sheer magnitude of the geography of East L.A. While the initial era of activist politics and early urban patterns emerged in South Texas prior to 1900, in particular San Antonio and El Paso, by the 1930s East L.A. had become not only an important component of Los Angeles but of urbanization patterns of barrios in the United States. In the Southwest, Chicana/o urbanism in California, especially in the southern sector of the state, has had a pronounced impact on the culture, economics, urbanization, and ethnic relations in this society.