Anti-Catholicism in the United States dates back to the colonial history of the U.S. Anti-Catholic attitudes were first brought to the Thirteen Colonies of British North America by Protestant settlers from Europe during the British colonization of the Americas. Two types of anti-Catholic rhetoric existed in colonial society and they continued to exist during the following centuries. The first type, derived from the theological heritage of the Protestant Reformation and the European wars of religion (16th–18th century), consisted of the biblical Anti-Christ and the Whore of Babylon variety and it dominated anti-Catholic thought until the late 17th century. The second type was a variety which was partially derived from xenophobic, ethnocentric, nativist, and racist sentiments and distrust of increasing waves of Catholic immigrants, particularly immigrants from Ireland, Italy, Poland, Germany, Austria and Mexico. It usually focused on the pope's control of bishops, priests, and deacons.
Historians have studied the motivations for American anti-Catholicism. The historian Arthur M. Schlesinger Sr. characterized prejudice against Catholics as "the deepest bias in the history of the American people." John Higham described anti-Catholicism as "the most luxuriant, tenacious tradition of paranoiac agitation in American history". Joseph G. Mannard says that wars reduced anti-Catholicism: "enough Catholics supported the War for Independence to erase many old myths about the inherently treasonable nature of Catholicism. ... During the Civil War, the heavy enlistments of Irish and Germans into the Union Army helped to dispel notions of immigrant and Catholic disloyalty."