America's 'mainline' churches may be named after Philadelphia's railway suburbs
In 1970 mainline Protestant churches claimed most American Protestants and over 30 percent of the whole population. By 2009 they had fallen to about 15 percent of adults. Even the label is telling: it arose in 1920s fights with fundamentalists and may come from the Main Line, a string of wealthy Philadelphia suburbs.
Mainline, sometimes called oldline or modernist, Protestantism refers to long-established denominations in the United States and Canada that lean theologically liberal or progressive. They stand in contrast to evangelical, fundamentalist and charismatic churches, historically Black denominations and the fast-growing Protestant churches of the Global South. They tend to emphasise social justice alongside personal salvation, cooperate through bodies such as the National Council of Churches, and are called ecumenical Protestants in much of the world.
The core is often labelled the 'Seven Sisters of American Protestantism', a phrase apparently coined by historian William Hutchison. The United Methodist Church is the biggest, with nearly 5.04 million US members in 2024, followed by the Evangelical Lutheran Church in America. The Episcopal Church, American Baptist Churches USA, the Presbyterian Church (USA), the United Church of Christ and the Disciples of Christ complete the group, the last with about 278,000 members as of 2022. Canada has parallels in the United Church of Canada and the Anglican Church of Canada.
The geography remains old-fashioned: most mainline members still live in the Northeast and Midwest. By 2025 the Public Religion Research Institute counted roughly 13 percent of Americans as white non-Hispanic mainline Protestants. Critics have long argued the very name carries elitist, White Anglo-Saxon assumptions, since for most of the twentieth century it described almost exclusively white, non-evangelical Protestants while implying they were the mainstream.
Terminology varies abroad. In Britain and Australia the phrase is rarely used, and academics distinguish mainline from 'mainstream Christianity', which usually means Trinitarian belief shared by Catholics, the Orthodox and evangelicals alike. Boundaries blur too: historically Black churches are usually classed separately, yet in 2014 the Christian Century argued that denominations such as the African Methodist Episcopal Church, with some 2.5 million members, fit the mainline description.
Source: Mainline Protestant
