People of Mexican descent and Anglo Americans have lived together in the U.S. Southwest for over a hundred years, yet relations between them remain strained, as shown by recent controversies over social services for undocumented aliens in California. In this study, covering the Spanish colonial period to the present day, Martha Menchaca delves deeply into interethnic relations in Santa Paula, California, to document how the residential, social, and school segregation of Mexican-origin people became institutionalized in a representative California town. Menchaca lived in Santa Paula during the 1980s, and interviews with residents add a vivid human dimension to her book. She argues that social segregation in Santa Paula has evolved into a system of social apartness—that is, a cultural system controlled by Anglo Americans that designates the proper times and places where Mexican-origin people can socially interact with Anglos. This first historical ethnographic case study of a Mexican-origin community will be important reading across a spectrum of disciplines, including anthropology, sociology, race and ethnicity, Latino studies, and American culture.