This study examines the creation of Black communities in the context of the Exoduster movement, the first major migration of African Americans out of the southern and border states. We focus initially on Nicodemus, Kansas, a site with well-preserved archival information, and then turn to census microdata on roughly three-hundred African-American communities that emerged in Kansas, Colorado, and Oklahoma between 1880 and 1920. Analysis of these communities informs a general model of minority-majority group relations that is differentiated along two dimensions: spatial segregation and the distinctiveness of business activities. Under conditions of prejudice from the majority ethno-racial group, the model predicts that rates of minority business proprietorship and community growth will increase with segregation and distinctiveness, but that the joint occurrence of these conditions presents an existential threat. We draw conclusions for the trajectories of several well-known Black communities, including Nicodemus, Tulsa, and Langston, Oklahoma.