This paper tests the hypothesis that 1935-80 U.S. migration patterns both within and between metropolitan and nonmetropolitan areas and regions and migrant/nonmigrant educational differences reflect regional changes in socioeconomic development and settlement patterns. Gross migration flows support the mobility transition hypothesis and the idea that developmental changes in metropolitanization structure the context of migration. Since the Great Depression, socioeconomic transformations of the periphery have reduced differences in migration patterns between the periphery and core regions. While migrants still have more education than nonmigrants, their differences vary systematically by regional socioeconomic development. Specifically, migrant/nonmigrant educational differences are (1) similar at origin and destination when both are at similar levels of socioeconomic development; (2) lower at the origin if the origin is higher in socioeconomic development; and (3) higher at the origin if the destination is higher in socioeconomic development.