This link can perhaps help. It's about the African-american migrations to the Great Plains and the foundations of "black towns" by voluntary migrants.
http://plainshumanities.unl.edu/encyclopedia/doc/egp.afam.006
By 1881 African Americans emigrants had established twelve agricultural colonies in Kansas: Nicodemus, Hodgeman, Morton City, Dunlap, Kansas City–area Colony, Parsons, Wabaunsee, Summit Township, Topeka-area Colony, Burlington, Little Coney, and the Daniel Votaw Colony
More African Americans settled in Oklahoma Territory with the land run of 1889, which ordered "free land" to non-Indians. [...]
In Oklahoma and Kansas, African Americans lived relatively free from the prejudices and brutality common in racially mixed communities of the Midwest and the South. Cohesive all-black settlements offered residents the security of depending on neighbors for financial assistance and the economic opportunity provided by access to open markets for their crops. [...]
The all-black towns were, for the most part, small agricultural centers that gave nearby African American farmers a market for their cotton and other crops. The Depression devastated these towns, and residents moved west or migrated to metropolises where jobs might be found. Black towns dwindled to only a few residents.
As a POD, there were two very important race riots during the Reconstruction Period (1865 - 1877) : 1866 riots in Memphis (May 1 to 3) and New Orleans (July 30). What if those riots were more violent or expanded to other cities due to inept generals/governors, wrong policies of the Freedmen's Bureau or President Johnson's vision?
In OTL, the outcome of the riots was to increase support for Radical Reconstruction. The Radical Republicans swept the congressional elections of 1866, obtaining a veto-proof majority in Washington. Subsequently, they passed key pieces of legislation, such as the Reconstruction Acts, Force Acts, and the Fourteenth Amendment of the United States Constitution which guaranteed citizenship, equal protection of the laws, and due process to former slaves. The change in political climate, catalyzed by response to the race riots, ultimately enabled former slaves to obtain the full rights of citizenship.
You could create two Homestead Acts in 1866 : the "Southern Homestead Act of 1866" and a "Kansas and Oklahoma territories Homestead Act". Those acts would open acres of public land for sale in the Southern states of Alabama, Arkansas, Florida, Louisiana, Mississippi
and in the territories of Kansas and Oklahoma. The bills specify, only free Blacks and loyal Whites would be allowed access to these lands.
The "Kansas and Oklahoma territories Homestead Act" would grant a "free land" to African Americans in order to create agricultural colonies and settlements. The primary beneficiaries for the first 5 years would be freedmen who were in desperate need of land to till. They would be followed by loyal Whites and later Chinese (after the surge of anti-Chinese riots).
Those settlements would be under the protection of the federal government, which means federally administrated, in order to protect African-american settlers. Those settlements will probably expand with new migrants trying to escape to Jim Crow laws. I imagine them as federal territories, counties and towns, similar to Washington DC, under the exclusive jurisdiction of the Congress and not a part of any U.S. state, even after the creation of Oklahoma and Kansas states (perhaps colloquially rebaptised with new names).