Jim Crow The system of racial segregation that developed in the post–Civil War South and extended well into the twentieth century; it replaced slavery as the chief instrument of white supremacy. Jim Crow laws segregated African Americans in public facilities such as trains and streetcars and denied them basic civil rights, including the right to vote. It was also at this time that the doctrine of “separate but equal” became institutionalized. (pp. 519, 588, 704, 705)