In 1682, William Penn founded the city to serve as capital of the Pennsylvania Colony. During the American Revolution, Philadelphia played an instrumental role as a meeting place for the Founding Fathers of the United States, who signed the Declaration of Independence in 1776 and the Constitution in 1787. Philadelphia was one of the nation'scapitals during the Revolutionary War, and the city served as the temporary U.S. capital while Washington, D.C., was under construction. During the 19th century, Philadelphia became a major industrial center and railroad hub that grew from an influx of European immigrants. It became a prime destination for African Americans during the Great Migrationand surpassed two million occupants by 1950. Following numerous civil rights protests and riots, the city experienced decades of heavy crime and neared bankruptcy by the 1980s. Revitalization began in the 1990s, with gentrificationturning around many neighborhoods and reversing its decades-long trend of population loss.