In the United States, evangelicalism is a movement among Protestant Christians who believe in the necessity of being born again, emphasize the importance of evangelism, and affirm traditional Protestant teachings on the authority as well as the historicity of the Bible. Comprising nearly a quarter of the U.S. population, evangelicals are a diverse group drawn from a variety of backgrounds, including nondenominational churches, Pentecostal, Baptist, Reformed, Methodist, Mennonite, Plymouth Brethren, and Quaker.
Evangelicalism has played an important role in shaping American religion and culture. The First Great Awakening of the 18th century marked the rise of evangelical religion in colonial America. As the revival spread throughout the Thirteen Colonies, evangelicalism united Americans around a common faith. The Second Great Awakening of the early 19th century led to what historian Martin Marty calls the "Evangelical Empire", a period in which evangelicals dominated U.S. cultural institutions, including schools and universities. Evangelicals of this era in the northern United States were strong advocates of reform. They were involved in the temperance movement and supported the abolition of slavery, in addition to working toward education and criminal justice reform. In the southern United States, evangelicals split from their northern counterparts on the issue of slavery, establishing new denominations that opposed abolition and defended the practice of racial slavery upon which the South's expanding cash-crops-for-export agricultural economy was built. During the Civil War, each side confidently preached in support of its own cause using Bible verses and Evangelical arguments, which exposed a deep theological conflict that had been brewing for decades and would continue long after Lee's surrender at Appomattox.