Introduction Many centers of crop domestication and diver- sity are experiencing rapid changes in agriculture practices resulting in the loss of crop varieties and the knowledge and customs that have sustained them (Brush 2004; Harlan 1975). Germplasm diversity is threatened by several factors includ- ing: replacement by high-yielding varieties, a shift to cash crop cultivation, change in land use, eco- nomic incentives to migrate or work off-farm, market integration, a dramatic reduction in the proportion of the population that farms, and in- frastructure development (Aguirre et al. 2000; Bellon 2000; Serratos-Hernández 2002; Van Dusen 2000; Zimmerer 1991, 1996). Thus, more economically developed areas may have a greater probability of a loss of traditional land- races (Aguirre et al. 2000). In this paper, we ex- amine sites of early maize (Zea mays) collection (undertaken in the 1940s and 1950s) to assess persistence of traditional varieties in an area of rapid agricultural and socioeconomic change. Since the development of modern (high-yield- ing or commercial hybrid) crop varieties (MVs), there has been a concern that these are replacing the genetic diversity of important food crops (Harlan 1975; Plucknett et al. 1983). Many pro- Describing Maize (Zea mays L.) Landrace Persistence in the Bajío of Mexico: A Survey of 1940s and 1950s Collection Locations 1 K. J. Chambers 2,* , S. B. Brush 3 , M. N. Grote 4 , and P. Gepts 5 2 Geography Graduate Group, University of California, Davis, One Shields Ave, Davis, CA 95616. 3 Human and Community Development, University of California, Davis, One Shields Ave, Davis, CA 95616. 4 Department of Anthropology, University of California, Davis, One Shields Ave, Davis, CA 95616. 5 Agronomy and Range Science, University of California, Davis, One Shields Ave, Davis, CA 95616. * Corresponding author: Phone: 530-750-7820; e-mail: kimberlee_chambers@yahoo.ca. Describing Maize (Zea mays L.) Landrace Persistence in the Bajío of Mexico: A Survey of 1940s and 1950s Collection Locations. Passport data for Mexico’s Guanajuato State were used to locate the sites where maize was collected in the 1940s and 1950s in an effort to document and conserve diversity. A map presenting survey points illustrates that collections have occurred repeatedly in the same locations. Observations of these locations reveal that urbanization and industrialization, not high yielding varieties, are displacing traditional vari- eties. Non-linear principal components analysis was used to assess associations between variables in areas where maize persists. Landraces appear to be associated with mountains and mesas, mixed cropping, little or no access to irrigation and areas classified as having low agricultural capacity; conversely, landraces have more commonly been replaced in areas of high agricultural capacity. The areas of high agriculture capacity, located in the riparian areas and plains, also have been the easiest to develop for urban and industrial use. Increasingly high rates of urbanization and development in areas of high agriculture capacity will impede the conservation of crop diversity in these areas. Key Words: Maize, crop diversity, in situ conservation, ex situ conservation, the Bajío, non-linear principal components analysis, Mexico, economic development, urbanization, in- dustrialization, landraces, hybrid crops Economic Botany, 61(1), 2007, pp. 60–72. © 2007, by The New York Botanical Garden Press, Bronx, NY 10458-5126 U.S.A. 1 Received 3 March 2006; accepted 28 November 2006.