A study measuring religious bodies in the United States called the, "2010 U.S. Religious Census: Religious Congregations; Membership Study (RCMS)" was recently released by the Association of Statisticians of American Religious Bodies (ASARB). The most comprehensive study of its kind, it provides detailed county-by-county information on congregations, members, adherents and attendance for 236 different faiths groups. (The survey differentiates between specific denominations within the same tradition.)
The researchers found Utah to be the most Christian* state with around 78 percent of population identifying as Christian adherents. The researchers found Maine to be the least Christian state with only about 27 percent identifying as Christian adherents.