I don’t know if the ARIS Survey puts exactly the same boundaries on US Regions as the UUA does, but regional findings from this survey are pretty interesting.
In 1990, the Northeast contained 21% of the American Population and 26% of the UU’s. (Remembering that this survey counted as UU anyone who claimed that, which was a lot more people than are actual members of churches.) The Northeast area shrank in population, and in 2008, contained 18% of the population and 19% of the UU’s. The Midwest lost less population (2%) but more UU’s (6%). The South gained 2% of the population and 3% of the UUs, and the west gained 3% of the population and a whopping 10% of the UU’s. Still…that’s a lot of growth. The upshot is that, as of 2008, this chart shows regional distribution of those claiming UU identity.