People of Irish descent form the largest ethnic group in the city of Philadelphia and its surrounding counties. The Irish have lived in Philadelphia since the pre-American Revolution period. Irishmen had participated in pro-Revolutionary activities in Philadelphia during the Revolutionary War. Like many American cities in the 19th century, Philadelphia, which was once a Quaker stronghold, changed dramatically with the influx of European immigrants. The first major influx of Irish came in 1844 from rural areas, spurred by the Irish Famine. Because of the Quaker belief and pledge of religious tolerance, Irish Catholics and Protestants, among others, made the city incredibly diverse. Philadelphia at the time had a need for industrial labor, and at the time Philadelphia was becoming a major industrial center in the United States. Irish took industrial positions. In the 1840s and 1850s, anti-Catholic sentiment grew against the Irish, and eventually led up to riots, such as the Philadelphia nativist riots and the Lombard Street riot. Eventually the Irish gained financial and social status in the latter half of the 19th Century and founded institutions during the period.