Over 7 million African Americans left the South for industrial cities in the North between 1915 and 1970, a period often referred to as the “Great Black Migration.” For black migrants, the North held the promise both of better-paying job opportunities and of social and political equality. During this period, and particularly between 1940 and 1970 when the majority of black migration occurred, the earnings of black men grew faster than those of white men nationwide. In 1940, black men earned a mean of 40 cents to the dollar earned by white men; by 1970, the black-to-white ratio had increased to 70 cents to the dollar. Although improvement in the quality and quantity of education for black students was the most important cause of the narrowing of this wage gap, migration to a higher-wage region also played a role. Even upon first arrival in northern cities, black migrants earned as much as blacks who were native to the North. Higher wages in the North represented a large economic gain for migrants; in 1940, for example, an average black worker in the North earned nearly three times as much as an average black worker in the South. Despite these gains, black migration to northern industrial cities did not create economic parity with whites for either the black migrants or their descendants. Although earnings for blacks relative to whites did rise at the national level, the black-white earnings ratio in the North remained about the same from 1940 to 1980, apart from a short-lived improvement in the late 1960s and early 1970s. This relative stagnation is generally explained by two forces on the demand side: a weakening of the American manufacturing sector after 1960, and racism in northern labor markets. In this article, I add a supply-side explanation to this story, detailing the labor market competition that new black migrants created for existing black residents in an economic setting already constrained by racism.