These immigrants were largely responsible for the first general strike in North America in 1835, in which workers in the city won the ten-hour workday. The city was a destination for thousands of Irish immigrants fleeing the Great Famine in the 1840s; housing for them was developed south of South Street, and was later occupied by succeeding immigrants. They established a network of Catholic churches and schools, and dominated the Catholic clergy for decades. Anti-Irish, anti-Catholic Nativist riots had erupted in Philadelphia in 1844. In the latter half of the century, immigrants from Russia, Eastern Europe and Italy; and African Americans from the southern U.S. settled in the city. Between 1880 and 1930, the African-American population of Philadelphia increased from 31,699 to 219,559. Twentieth-century black newcomers were part of the Great Migration out of the rural South to northern and midwestern industrial cities.

Who carried out the first strike in North America?