The 2010 U.S. Religion Census from the Association of Statisticians of American Religious Bodies reports that there are 19 religious groupings (or denominations) with at least 1 million adherents in the United States. Together, these account for 89.4 percent of all religious adherents. The next-largest 42 groupings, with between 100,000 and 1 million adherents, account for another 9.4 percent of all religious adherents.

But how widely distributed are these groups? Are they clustered in one region, or spread throughout the United States? One way to tell is by looking at how many counties each has a presence in.

There are 3,143 counties or county-equivalents in the United States. Of the 19 largest groups -- those with more than 1 million adherents -- here's how widely distributed they are:
  1. United Methodist Church (at least one congregation in 2,991 counties)
  2. Catholic Church (2,960 counties)
  3. Southern Baptist Convention (2,702 counties)
  4. Non-denominational Christian congregations (2,665 counties)
  5. Assemblies of God (2,563 counties)
  6. Churches of Christ (2,427 counties)
  7. Presbyterian Church (USA) (2,358 counties)
  8. Episcopal Church (2,049 counties)
  9. Latter-day Saints (Mormons) (1,873 counties)
  10. Seventy-day Adventist (1,827 counties)
  11. Lutheran Church--Missouri Synod (1,804 counties)
  12. Evangelical Lutheran Church in America (1,739 counties)
  13. Church of God (Cleveland, Tennessee) (1,598 counties)
  14. Christian Churches and Churches of Christ (1,580 counties)
  15. United Church of Christ (1,168 counties)
  16. American Baptist Churches (USA) (1,051 counties)
  17. African Methodist Episcopal Church (1,044 counties)
  18. National Baptist Convention (USA) (722 counties)
  19. Muslim congregations (592 counties)
One group of note: Non-denominational Christian churches. This group has rarely been counted in denominational surveys, yet it's one of the largest religious and most widely distributed groups in the United States. 

The boards and senior administrators of theological schools would do well to be aware of religious demographic information, and for U.S. schools, this mammoth and authoritative directory, with 726 pages, is a great place to start. It's available from

Image adapted from flickruser Paul Adams