, an old
Puritan meetinghouse currently used by a
Unitarian Universalist congregation While the term "mainline" was not applied to churches until the 20th century, mainline churches trace their history to the
Protestant Reformation of the 16th century. The largest and most influential Protestant denominations in Britain's
Thirteen Colonies were the
Anglicans (after the American Revolution called Episcopalians) and the
Congregationalists (from which the
Unitarians would later split). These were later surpassed in size and influence by other Protestants: the Baptists, Presbyterians and Methodists. Sharing a common Reformation heritage with Episcopal and Congregational churches, these denominations together created the mainline. It was, according to historian Jason Lantzer, "the emerging evangelical movement that would help forge the Seven Sisters and which provides a core to the wide variety of theological and doctrinal differences, shaping them into a more coherent whole." The
Great Awakening ignited controversy within Protestant churches between
Old Lights and New Lights (or
Old Side and New Side among Presbyterians). Led by figures such as the Congregationalist minister
Charles Chauncy, Old Lights opposed the evangelical
revivalism at the heart of the Awakening, while New Lights, led by fellow Congregationalist minister
Jonathan Edwards, supported the revivals and argued for the importance of having a
conversion experience. By the 1800s, Chauncy's followers had drifted toward forms of theological liberalism, such as
Universalism,
Unitarianism and
Transcendentalism. in
Church of the Good Shepherd, a 19th-century
Anglo-Catholic Episcopal Church in
Pennsylvania The
Second Great Awakening would inaugurate a period of evangelical dominance within American mainline Protestantism that would last over a century. The Second Great Awakening was a catalyst for the reform of society. Efforts to improve the rights of women, reforming prisons, establishing free public schools, prohibiting alcohol, and (in the North) abolishing slavery were promoted by mainline churches. After the
Civil War, however, tensions between evangelicals and non-evangelicals would re-emerge. As the practice of
historical criticism spread to the United States, conflict over
biblical inspiration erupted within Protestant churches. Conservative Protestants led by
A. A. Hodge,
B. B. Warfield and other
Princeton theologians argued for
biblical inerrancy, while liberal theologians such as
Charles A. Briggs of
Union Theological Seminary were open to using historical criticism to understand the Bible. As 19th–century evangelicals embraced
dispensational premillennialism and retreated from society in the face of mounting social problems caused by industrialization, urbanization and immigration, liberal Protestants embraced the
Social Gospel, which worked for the "regeneration of society" rather than only the conversion of individuals. The
Fundamentalist–Modernist Controversy of the 1920s widened the division between evangelical and non-evangelical Protestants as the two sides fought for control over the mainline denominations. The
fundamentalists lost these battles for control to the modernists or liberals. Since the 1920s, mainline churches have been associated with liberal Protestantism.
Episcopalians and
Presbyterian WASPs tend to be considerably wealthier and better educated than most other religious groups in America, and are disproportionately represented in the upper reaches of American
business, law and politics, and for many years were especially dominant in the
Republican Party. Numbers of the
wealthiest and most affluent American families, such as the
Vanderbilts and
Astors,
Rockefeller, who were Baptists,
Du Pont,
Roosevelt,
Forbes,
Fords, In 2020, Public Religion Research Institute conducted a religious census, based on self-identification, finding that an estimated 16% of U.S. Americans identified as non-Hispanic white mainline Protestants, slightly outnumbering non-Hispanic white evangelical Protestants who were 14% of the American population. In 2014, Pew Research completed and published the
Religious Landscape Survey in which it was estimated that 14.7% of American adults identified as mainline Protestant, excluding historically Black and African American denominations, while 25.4% identified as evangelical Protestants, also excluding membership in historically Black denominations. In 2025, Pew Research published an updated
Religious Landscape Survey, finding that 11% of American adults identified as mainline Protestant while 23% identified as evangelical Protestants. Mainline churches share an active approach to social issues that often leads to cooperation in organizations such as the
National Council of Churches. Because of their involvement with the
ecumenical movement, mainline churches are sometimes (especially outside the United States) given the alternative label of ecumenical Protestantism. These churches played a leading role in the
Social Gospel movement and were active in social causes such as the
civil rights movement and the
women's movement. As a group, the mainline churches have maintained religious doctrine that stresses
social justice and personal
salvation. Some also include the highest proportion of those with some college education, such as the
Episcopal Church (76%), and better educated than most other religious groups, and they were disproportionately represented in the upper reaches of US business and law until the 1950s. In the 1990s four of the US Supreme Court Justices were Mainline Protestants:
Sandra Day O'Connor,
John Paul Stevens,
William Rehnquist and
David Souter. From 1854 until at least 1964, Mainline Protestants and their descendants were heavily
Republican. In recent decades, Republicans slightly outnumber Democrats. From 1965 to 1988, mainline church membership declined from 31 million to 25 million, then fell to 21 million in 2005. While in 1970 the mainline churches claimed most Protestants and more than 30 percent of the population as members, today they are a minority among Protestants; in 2009, only 15 percent of Americans were adherents. ==Notes==