There were about 2.35 million Muslim adults and children living in the United States in 2007 – accounting for 0.8% of the U.S. population – when Pew Research Center began measuring this group’s size, demographic characteristics and views. Since then, growth has been driven primarily by two factors: the continued flow of Muslim immigrants into the U.S., and Muslims’ tendency to have more children than Americans of other faiths.

In 2015, the Center projected that Muslims could number 3.85 million in the U.S. by 2020 – roughly 1.1% of the total population. However, Muslim population growth from immigration may have slowed recently due to changes in federal immigration policy.

The number of Muslim houses of worship in the U.S. also has increased over the last 20 years. A study conducted in 2000 by the Cooperative Congregational Studies Partnership identified 1,209 mosques in the U.S. that year. Their follow-up study in 2011 found that the number of mosques had grown to 2,106, and the 2020 version found 2,769 mosques – more than double the number from two decades earlier.

Alongside their population growth, Muslims have gained a larger presence in the public sphere. For example, in 2007, the 110^th Congress included the first Muslim member, Rep. Keith Ellison, D-Minn. Later in that term, Congress seated a second Muslim representative, Rep. Andre Carson, D-Ind. The current 117^th Congress has two more Muslims alongside Carson, the first Muslim women to hold such office: Reps. Ilhan Omar, D-Minn., and Rashida Tlaib, D-Mich., first elected in 2018. ..Though many Americans have negative views toward Muslims and Islam, 53% say they don’t personally know anyone who is Muslim, and a similar share (52%) say they know “not much” or “nothing at all” about Islam. Americans who are not Muslim and who personally know someone who is Muslim are more likely to have a positive view of Muslims, and they are less likely to believe that Islam encourages violence more than other religions.

Source: Pew Research Center

For the first day of the 116^th Congress, here are five facts about the religious affiliation of members of Congress:

1) The religious composition of the new Congress is very different from that of the U.S. adult population. While the number of self-identified Christians in Congress has ticked down slightly, Christians as a whole – and especially Protestants and Catholics – are still overrepresented in proportion to their share in the general public. But by far, the largest difference between the U.S. public and Congress is in the share of people who are unaffiliated with a religious group. In the general public, 23% say they are atheist, agnostic or “nothing in particular.” In Congress, just one person says she is religiously unaffiliated – Sen. Kyrsten Sinema, D-Ariz., who was recently elected to the Senate after three terms in the House.

2) While Congress remains overwhelmingly Christian, the number of non-Christian members has risen to 63. Most non-Christian members of Congress are Jewish (34), but there are also two Buddhists, three Muslims, three Hindus, two Unitarian Universalists, one unaffiliated member and 18 who decline to specify a religious affiliation. Only two of the non-Christians – Jewish Reps. Lee Zeldin, R-N.Y., and David Kustoff, R-Tenn. – are Republicans. The rest are Democrats.

3) The largest change in the new Congress comes in the “unspecified/other” Protestant category, which gained 16 seats. (“Unspecified/other” Protestants include those who say they are Christian, evangelical Christian, evangelical Protestant or Protestant, without specifying a denomination.) Presbyterians and Anglicans/Episcopalians lost the most seats in the new Congress, with each losing nine.

4) There are fewer Christians in the incoming freshman class than there are among incumbents. In the new Congress, 96 freshmen will join 438 incumbents: the largest freshman class since 2011, when the 112th Congress was sworn in. While the share of Christians among the freshman class is still higher than among the general public (81% vs. 71%), it is lower than the share among incumbents (90%). Among the new members are the first two Muslim women in Congress, Reps. Rashida Tlaib, D-Mich., and Ilhan Omar, D-Minn.

5) Both chambers of Congress have roughly similar shares of Christians and non-Christians. But within those categories, there are some differences, particularly with regard to Catholics, who make up 32% of the House, but just 22% of the Senate. Additionally, all of the Muslims, Hindus and Unitarian Universalists are in the House.

Source: Pew Research Center