See above. It strikes me that much of the lands between the Pacific and the actual existent states were theoretically available for settlement and colonization by freed slaves, no matter the presence of natives. With that in mind, the question that must be asked:
What if as part of the Reconstruction, the freed blacks of the slave states were transported in great numbers west, to settle what would become states like California, Oregon, Montanna, etc... that these would be the "black" states, in a sense. They would have certain amount of protection and oversight by detachments of the United States Army and be given funds from appropriated wealth of southern plantation owners, but otherwise they're on their own until they get statehood.
How does this little experiment go?