The study addresses research questions about demographic, social, and economic characteristics of the joint U.S.-Mexico border region. The study sample consists of all of the counties and municipios in the U.S.-Mexico border region i.e. all those in the U.S. four border states (California, Arizona, New Mexico, and Texas), as well as those in the six Mexican border states (Baja California, Sonora, Chihuahua, Coahuila, Nuevo Leon, and Tamaulipas). There are 246 counties and 273 municipios in this region. The goal of this research is to understand the broader context of the border region and to compare the results to prior studies of the border region and its cities. It examines the levels of the 16 matched characteristics at the county and municipio level in the territory of the ten border states, The methods consist of definitional matching and descriptive spatial analysis and comparisons. The findings are summarized to answer the research questions. Do socioeconomic characteristics in the border region differ between the U.S. and Mexico? Do they differ between the eastern versus western borderlands? Do characteristics differ for the major metropolitan versus non-metropolitan areas of the borderlands? Are city to city differences (north to south) similar or different to region to region differences (north to south)? This paper seeks to answer these questions, discuss the findings, compare the results to prior work, and analyze the policy and planning implications. (C) 2001 Elsevier Science Inc. All rights reserved.