Protestants and other non-Catholic or Mormon Christians make up 51% of Americans, according to a 2013 Gallup survey, and the states that are most Protestant have over a 70% majority. Compare that to the most Catholic and most Mormon states whose religious majorities in their states are 54% and 60%, respectively.
Although Protestants are still in the majority in the U.S., their numbers are down from 54% in 2008. Interestingly, the most Protestant state, Mississippi at 77%, is also the most religious state; but the least Protestant state, Utah at 11%, is the second most religious state in America.
Here are the most and least Protestant states in the U.S.: