Copper ore sources exploited during the Late Postclassic Period (1300 to 1521 A.D.) were located by means of lead isotope analyses of copper ores from 15 deposits in West Mexico, Oaxaca, and Veracruz and of 171 copper artifacts from nine Mesoamerican archaeological sites in West Mexico and in southern, central, and northeastern Mesoamerica. West Mexican ores provided copper metal for most artifacts from the west Mexican settlements of Atoyac and Urichu, as well as for some artifacts from Aztec towns, Huastec centers, a Maya site, and settlements in Oaxaca and Chiapas. West Mexico was not marginal to Mesoamerican events but played the primary role in the production and distribution of copper and bronze artifacts, one of Mesoamerica’s key exotic goods.