The denomination had its origins in colonial times when members of the Church of Scotland and Presbyterians from Ireland first immigrated to America. After the American Revolution, the PCUSA was organized in Philadelphia to provide national leadership for Presbyterians in the new nation. In 1861, Presbyterians in the Southern United States split from the denomination because of disputes over slavery, politics, and theology precipitated by the American Civil War. They established the Presbyterian Church in the United States, often simply referred to as the "Southern Presbyterian Church". Due to its regional identification, the PCUSA was commonly described as the Northern Presbyterian Church. Despite the PCUSA's designation as a "Northern church", it was once again a national denomination in its later years.