Denominational Maps by County.
here for original, larger view, explanation and interpretation.
The colors each stand for the largest denomination in each county. Counties with more than 50% of the population belonging to a specific denomination are marked with a plus (notice Utah area, Southern Texas, Northern Texas and several areas around the South, as well as Garrison Keillor Lutheran land)
One of the things I find intriguing is the deep red aerial view of the Bible Belt.
My area (larger investors in Notre Dame football than in the local college teams, by the way) is largely Catholic. No surprise, even in the home and hub of the megachurch. What of yours?
h/t to MarkO