Ruling out legal segregation shifted ghettoization northward and sped it up.

Evidence

In the South with its “Jim Crow” laws, the strategy adopted was to enforce residential segregation through laws. In 1910 the Baltimore city council established separate neighborhoods for blacks and for whites. Similar laws were passed in other cities, including Atlanta, Louisville, St. Louis, Oklahoma, and New Orleans. However, in 1917, the Supreme Court declared this procedure unconstitutional. Thereafter the residential segregation of African Americans into extensive ghettos developed more quickly in the North, with Chicago and Cleveland the first. — David Theo Goldberg, John Solomos, A Companion to Racial and Ethnic Studies, 2385