Most Americans identify as Christian (about 77 percent according to a Gallup poll), making Christianity the largest religion in the United States. But, when looking at the religions people identify with outside of Christianity, the results get pretty interesting.
The Association of Statisticians of American Religious Bodies(ASARB), which sponsors the US Religon Census every 10 years, mapped out the religions Americans adhere to across the country. ASARB also looked at the second largest religions across each state based on census data. The results of that data show that Islam is the second largest religion in 20 states, mainly across the South and Midwest, while Buddhism is the second largest religion in 13 states, mostly in the West. Judaism is the second largest religion in the District of Columbia and 14 states, mostly located in the Northeast. Hindu and Baha’i are also represented as the second largest religions in Arizona and South Carolina respectively.
Here is a look at that map:
Here is a look at the second largest religions by county:
Mark Silk of Religion News Service, however disputed the census data on the second largest religions, pointing to a 2008 Pew Religious Landscape Study that shows Judaism as the second largest religion.
Altogether, Jews come in second in at least half the states (not 15); Muslims, in at most a dozen (not 20), and Buddhists, in the remainder (throughout most of the West). The reason for the principal discrepancy (between Jews and Muslims) is that the U.S. Religious Census relies on reports of actual synagogue membership, and many self-identified Jews don't belong to synagogues; while the reporting Muslim bodies provide estimates of mosque membership.
Silk also noted that the Pew study found other religions represent less than 5 percent of Americans’ religious affiliations, while more people (about 16 percent) don’t even identify with any religion.
More religion maps and data based off the 2010 Census can be viewed here.
(H/T The Washington Post)