Map of Leading Church Bodies in 2000

Data collected by The Glenmary Research Center. The GRC is a catholic group that supports the Glenmary Home Missioners.... who are domestic missioners. So the point of this data collection was to find out where to where to concentrate their efforts. They have some other maps available (in PDF format), including U.S. Counties With High Percentages of Unclaimed/Unchurched, U.S. Counties With High Percentages of African Americans, and others that I find interesting. I guess they've been around around for a while. Take a look at this map from 1938: