Religion in the United States is remarkable in its high adherence level compared to other developed countries. The First Amendment to the country's Constitution prevents the government from having any authority in religion, and guarantees the free exercise of religion. Many faiths have flourished in the United States, including imports spanning the country's multicultural heritage as well as those founded within the country, and have led the United States to become the most religiously diverse country in the world.

Demographics The majority of Americans identify themselves as Christians (65% as of 2019), while non-Christian religions (including Islam, Judaism, Hinduism, and others) collectively make up about 6% of the adult population. Another 26% of the adult population identified as having no religious affiliation. A majority of Americans report that religion plays a "very important" role in their lives, a proportion unusual among developed nations, though similar to other nations in the Americas. According to the American Religious Identification Survey, religious belief varies considerably across the country: 59% of Americans living in Western states report a belief in God, yet in the South (the "Bible Belt") the figure is as high as 86%.Frank Newport Belief in God Far Lower in Western U.S.; Overall, 78% believe in God, 15% in a higher spirit July 28, 2008 News.gallup.com

The United States has more Christians than any other country in the world (US is the largest Christian nation in respect to population). Going forward from its foundation, the United States has been called a Protestant nation by a variety of sources.Tri-Faith America: How Catholics and Jews Held Postwar America to Its Protestant Promise by Kevin M. Schultz, p. 9Obligations of Citizenship and Demands of Faith: Religious Accommodation in Pluralist Democracies by Nancy L. Rosenblum, Princeton University Press, 2000 - 438, p. 156The Protestant Voice in American Pluralism by Martin E. Marty, chapter 1 This is despite the fact that Protestants are no longer the majority in the United States (43%).

Religion and political identity Politicians frequently discuss their religion when campaigning, and many churches and religious figures are highly politically active. As important as religion is in politics, Thomas Jefferson, the third president of the United States, had to fight his way into office due to his controversial thoughts about religion. His writing was often seen as anti-Christian. It is argued that Jefferson's win can be linked to him changing the election's narrative from one about his own religious beliefs, to one about his tolerance of religious freedom (Lambert).Lambert, F. (1997). `God-and a religious president... [or] Jefferson and no God': for a voter-imposed. Journal of Church & State, 39(4), 769. Retrieved from EBSCOhost.

There are Christians in both the Democratic Party and the Republican Party, but evangelical Christians and conservative Catholics tend to support the Republican Party whereas more liberal Protestants, Catholics and secular voters tend to support the Democratic Party. A 2019 survey conducted by Pew Research Center found that 54% of adults believe the Republican Party to be "friendly" toward religion, while only 19% of respondents said the same of the Democratic Party.

Every President and Vice President, was raised in a family with affiliations with Christian religions. Only former Presidents John F. Kennedy and Joe Biden were raised in Roman Catholic families. Two former presidents, Richard Nixon and Herbert Hoover, were raised as Quakers. All the rest were raised in families affiliated with Protestant Christianity. However, many presidents have themselves had only a nominal affiliation with churches, and some never joined any church.

While fundamentalist religious people are less likely to have information collected about who they will vote for, they "tend to engage mainstream political activity at higher rates than the average American".Sherkat, D. E. (2007). Religion and Survey Non-Response Bias: Toward Explaining the Moral Voter Gap between Surveys and Voting. Sociology Of Religion, 68(1), p.93 Retrieved from EBSCOhost. While there is a common belief that religious voters will always vote Republican that is not necessarily the case. Whether the vote is made for one party or another is noticeably based on socioeconomic status.(Hirschl, T. A., Booth, J. G., & Glenna, L. L. (2009). The Link Between Voter Choice and Religious Identity in Contemporary Society: Bringing Classical Theory Back In. Social Science Quarterly, 90(4), 931. Retrieved from EbscoHost For low income religious people, there is almost no correlation between their religious beliefs and their voting decision.Hirschl, T. A., Booth, J. G., & Glenna, L. L. (2009). The Link Between Voter Choice and Religious Identity in Contemporary Society: Bringing Classical Theory Back In. Social Science Quarterly, 90(4), 941. Retrieved from EbscoHost George W. Bush, a Methodist, earned a slim victory over John Kerry, with voters who cited "moral values" (a commonly used term among religiously-inclined voters) playing a crucial part in the election. Bush's clear victory has been directly attributed to fundamentalist Christian groups.Sherkat, D. E. (2007). Religion and Survey Non-Response Bias: Toward Explaining the Moral Voter Gap between Surveys and Voting. Sociology Of Religion, 68(1), 83-95.p. 94 Retrieved from EBSCOhost.

In 2006 Keith Ellison became the first Muslim elected to the federal government, as the representative of Minnesota's 5th congressional district. When re-enacting his swearing-in for photos, he used the copy of the Qur'an once owned by Thomas Jefferson.

In 2006, PRRI found that 54% of Democrats identified as Protestants. A Gallup Poll released in 2019 indicated that 60% of Americans would be willing to vote for an atheist as president. Research shows that candidates that are perceived to be religious are considered more trustworthy. A 2020 PRRI American Values Survey found that of Democratic voters, 42% were Protestant while 23% identified as Catholic. The same survey found that of Republican voters, 54% were Protestant while only 18% were Catholic. A November 2024 Politico Poll found that Evangelicals outnumbered Catholics among Harris and Trump voters. The 2023-2024 Pew Religious Landscape Study found that 51% of Democrats were Christian and mostly Protestant.

Separation of church and state

In the 1780-1820s in New England the dominant Federalist Party was closely linked to the Congregational church; when the party collapsed, the church was disestablished.Kelly Olds, "Privatizing the church: disestablishment in Connecticut and Massachusetts." Journal of Political Economy (1994): 277-297. in JSTOR In 1800, and other elections, Federalists targeted infidelity in any form. They repeatedly charged that Republican candidates, especially Thomas Jefferson himself, were atheistic or nonreligious.Jonathan J. Den Hartog, Patriotism and Piety: Federalist Politics and Religious Struggle in the New American Nation (2015). Conversely, the Baptists, Methodists the other dissenters and the religiously nonaligned, favored the Republican cause.Amanda Porterfield, Conceived in Doubt: Religion and Politics in the New American Nation (2012) The Baptists, in particular, made the disestablishment one of their founding principles.William G. McLoughlin, New England dissent, 1630-1833: the Baptists and the separation of church and state (Harvard University Press, 1971). Hence Jefferson chose the Baptists of Connecticut to pronounce there should be a "wall of separation" between church and state.Constance B. Schulz, "'Of Bigotry in Politics and Religion': Jefferson's Religion, the Federalist Press, and the Syllabus." The Virginia Magazine of History and Biography 91#1 (1983): 73-91. in JSTOR

The separation of church and state is a legal and political principle which advocates derive from the First Amendment to the United States Constitution, which reads, "Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof". The phrase "separation of church and state", which does not appear in the Constitution itself, is generally traced to an 1802 letter by Thomas Jefferson to the Danbury Baptists, where Jefferson spoke of the combined effect of the Establishment Clause and the Free Exercise Clause of the First Amendment. It has since been quoted in several opinions handed down by the United States Supreme Court.Jefferson's Danbury letter has been cited favorably by the Supreme Court many times. In its 1879 Reynolds v. United States decision the high court said Jefferson's observations "may be accepted almost as an authoritative declaration of the scope and effect of the [First] Amendment". In the court's 1947 Everson v. Board of Education decision, Justice Hugo Black wrote, "In the words of Thomas Jefferson, the clause against establishment of religion by law was intended to erect a wall of separation between church and state."

Robert N. Bellah has argued in his writings that although the separation of church and state is grounded firmly in the constitution of the United States, this does not mean that there is no religious dimension in the political society of the United States. He argued that in effect there is an American civil religion which is a nonsectarian faith with sacred symbols drawn from national history. Scholars have portrayed it as a cohesive force, a common set of values that foster social and cultural integration. Bellah's 1967 article analyzes the inaugural speech of John F. Kennedy: "Considering the separation of church and state, how is a president justified in using the word 'God' at all? The answer is that the separation of church and state has not denied the political realm a religious dimension." From the issue entitled Religion in America.

Catholics

Catholics represent the largest Christian denomination in America with over 68 million members.The Official Catholic Directory 2009. 85% of these Catholics found their faith to be "somewhat" to "very important" to them. In recent national elections Catholics cast 25 to 27 percent of the ballots.CARA's New Book Identifies Trends in U.S. Catholic Church , Catholicism USASecular and Security-Minded: The Catholic Vote in Summer 2008 , A National Opinion Survey of Likely Catholic Voters, Executive Summary, BELDEN RUSSONELLO & STEWART, August 2008

Members of the Catholic Church have been active in the politics of the United States since the mid 19th century. The United States has never had an important religious party (unlike Europe and Latin America). There has never been a Catholic religious party, either local, state or national.

In 1776 Catholics comprised less than 1% of the population of the new nation, but their presence grew rapidly after 1840 with immigration from Germany, Ireland, Italy, Poland, and elsewhere in Catholic Europe from 1840 to 1914, and also from Latin America in the 20th century. Catholics now comprise 25% to 27% of the national vote, with over 68 million members today. 85% of today's Catholics report their faith to be "somewhat" to "very important" to them.

From the mid-19th century down to 1964 Catholics were solidly Democratic, sometimes at the 80%-90% level. Religious tensions were major issues in the presidential elections of 1928 when the Democrats nominated Al Smith, a Catholic who was defeated. Catholics formed a core part of the New Deal Coalition, with overlapping memberships in the Church, labor unions, and big city machines, and the working class, all of which promoted liberal policy positions in domestic affairs and anti-communism during the Cold War. Since the election of a Catholic President in 1960, Catholics have split about 50-50 between the two major parties in national elections.