Between 1893 and 1920 the rising tide of racial antagonism and discrimination that swept America fundamentally altered racial relations in the United States Navy. African Americans, an integral part of the enlisted force since the Revolutionary War, found their labor devalued and opportunities for participation and promotion curtailed as civilian leaders and white naval personnel made repeated attempts to exclude blacks from the service. Between 1920 and 1942 the few black sailors who remained in the navy found few opportunities. The development of Jim Crow in the U.S. Navy occurred in three phases. During the first, between 1893 and 1919, a de facto policy excluded African Americans from all ratings save those of the messman's branch. The second major phase began in April 1919 with the cessation of domestic enlistments in the messman’s branch. The meant the effective exclusion of blacks, as the navy had previously limited them to this one area of service. Between World War I and 1933 thousands of East Asians enlisted as messmen and stewards, replacing native-born Americans. The third phase, between 1933 and 1942, represented a qualified step forward for blacks as the navy again began to recruit them, though it limited them to the messman branch. In their circumscribed roles on board ship, black messmen and stewards suffered discrimination and possessed few opportunities for advancement. In the late-1930’s and early-1940’s public figures, including prominent leaders of the African American community, charged the navy, army, and defense industries with practicing racial discrimination. The navy, reflecting its general conservatism, responded slowly to demands for change. By 1942, however, the navy began detailing black men to billets outside the messman’s branch, a first step away from Jim Crowstyle policies. This thesis analyzes the evolution of discriminatory and exclusionary enlistment policies in the navy. While others have provided the basic outline of segregation in the navy, this thesis provides a more complete analysis of the navy’s actions in the context of wider American society. This thesis also confirms that the navy was a slow-moving actor which followed the society’s lead and did not substantially revise existing racial hierarchy.