From the 2010 US Religious Census.
The Restoration Movement churches -- which are only very loosely organized -- had 5,293 U.S. congregations and 1.45 million adherents in 1,580 counties in 2010. The churches were most clustered in a belt from Northern Kentucky (where, notably, the revival that marks the beginning of the movement happened in 1801), through central Indiana and Illinois, and through Missouri and Kansas, parts of Nebraska and Oklahoma, and into Eastern Colorado.
They were also well represented in Oregon, parts of Virginia and East Tennessee, Central Florida, and in a southern ring around the City of Atlanta.
There were none, apparently, in North Dakota.