Nicodemus, Kansas was founded by freedmen during the reconstruction period - 1877. Not aware of any others.

A number of towns in Oklahoma were settled and run by black people from the South after the fall of Reconstruction. These were mostly farming towns, and the largest and most famous example is probably Boley.

Black Oklahomans were disenfranchised after Oklahoma adopted segregationist laws during the 1910s, and the Great Depression and Dust Bowl affected these towns very badly as well. Many of them, including Boley, still exist as majority-black communities.

I'm editing this to add that it's not correct for me to suggest that these towns were founded to get unwanted people out of other parts of the country. Rather, they were founded by African Americans for African Americans who wanted to farm their own land and not be subjected to the racist laws of the post-Reconstruction South.