- Taken together, nondenominational and independent churches may now be considered the third largest religious group in the country, with 12.2 million adherents in 35,500 congregations. Only the Catholic Church and the Southern Baptist Convention are larger.
- The U.S. was home to 2,106 mosques nationwide in 2010. The figure includes 166 mosques in Texas, 118 in Florida and 50 Muslim houses of worship in North Carolina.
- Buddhist congregations were reported in all 50 states, and Hindu houses of worship in 49 states.
The study data and the accompanying maps, which provide easy visual analysis of religion demographics, are widely used by scholars, researchers, teachers, the media and the general public.
"Each year the ARDA disseminates thousands of copies of the data files and each week thousands of visitors use ARDA's online maps and reports to explore America's religious landscape," said sociologist Roger Finke of Pennsylvania State University, ARDA director. "Whether it is county profiles conducted by local churches or national research conducted by religion scholars, the data offer a trove of new information on American religion."
One limitation of the study is that information on attendance and membership is self-reported by the religious bodies. Some figures are estimates, such as the 2.6 million Muslims in the U.S. Further information on study sources is available on ARDA.
Still, Clifford Grammich, a study leader, said the 2010 study "is the most comprehensive local-level analysis of U.S. religious adherents and attendance in more than 60 years."
What emerges from the new census is a portrait of an increasingly diverse, vital religious marketplace.
It is difficult today for any one group to claim a monopoly on a particular state or region of the country.
For example, if you consider, as the group itself does, that the Mormon Church is a Christian body, The Church of Jesus Christ of Latter-day Saints reported the largest increase among Christian groups from 2000 to 2010 in 30 states, including places like North Dakota, New Mexico and West Virginia.
Meanwhile, the census found nondenominational and independent churches in 2,663 counties, or 88 percent of U.S. counties. Added together, they would be among the top five religious groups in 48 states.
In secular terms, Hartford Seminary sociologist Scott Thumma compares the nationwide growth of groups such as the Mormon Church and nondenominational congregations to successful fast-food franchises starting out locally, finding they meet a need and then expanding regionally and nationally until you can find one at almost every rest stop.
Nondenominational churches, in particular, have become "an alternative to denominational religiosity in every market," Thumma said.
The diversity extends beyond Christianity.
The number of non-Christian congregations -- synagogues, mosques, temples and other religious centers -- increased by nearly a third, from 8,795 in the 2000 study to 11,572 in the 2010 census. Houses of worship of other faiths were found in 985 counties in 2010, almost a third of the total.
Even some groups that had a drop in adherents found themselves expanding in newer markets.
For example, the Catholic Church, which had 62 million adherents in 2000 and 59 million in 2010 according to the census, reported the largest gains among Christian groups in 11 states, including Georgia, Nevada and Oregon.
Even places such as Salt Lake County in Utah, the home of the Latter-day Saints, have become more diverse, cosmopolitan communities, census researchers noted. The number of Catholic adherents there jumped from 53,500 to 84,000 from 2000 to 2010.
There has been a shift to "a true marketplace," Thumma said. When new players "in the religious marketplace come along, it's harder to maintain this is our market, you can't come in here."
So, too, is it possible for a Mormon to run for president.
It is "absolutely the case," Thumma said, that the spread of Latter-day Saints across the nation, and the degree of familiarity that provided many Americans with their faith, paved the way for a Romney run.
David Briggs writes the Ahead of the Trend column for the Association of Religion Data Archives.