Between 1900 and 1934 the African American population in Chicago grew from 30,000 to 236,000. The population was initially diluted in scattered places, but during this time, due to the change in the demographics of Chicago, it became concentrated in two large strips of land. The racial concentration was enforced by violence for few decades, until restrictive covenants became the preferred way to enforce segregation. Although they were previously rare, racially restrictive covenants among property owners that outlawed the purchase, lease, or occupation of their properties by African Americans became common in Chicago in the 1920s following the Great Migration, especially after the 1926 United States Supreme Court upheld racially restrictive covenants in Corrigan v. Buckley ().