Average annual earnings calculated from the census of manufactures are used to extend previous research on labor market integration in the United States. In contrast to earlier research examining occupational wage rates, census average earnings indicate that a well-integrated labor market had emerged in the Northeast and North Central regions as early as 1879. They also reveal substantial convergence within the South Atlantic and South Central regions, suggesting the emergence of a unified southern labor market. Large and persistent North-South differentials indicate, however, that a unified national labor market did not develop before World War I.