Harrisburg (, Pennsylvania German: Harrisbarrig) is the capital city of the U.S. commonwealth of Pennsylvania and the seat of Dauphin County. With a population of 50,099 as of 2020, Harrisburg is the ninth-most populous city in Pennsylvania. It is the larger principal city of the Harrisburg–Carlisle metropolitan statistical area, also known as the Susquehanna Valley, which had a population of 591,712 in 2020 and is the fourth-most populous metro area in Pennsylvania. Harrisburg is situated on the east bank of the Susquehanna River and is located 83 miles (134 km) southwest of Allentown and 107 miles (172 km) northwest of Philadelphia. Harrisburg played a role in American history during the Westward Migration, the American Civil War, and the Industrial Revolution. During part of the 19th century, the building of the Pennsylvania Canal and later the Pennsylvania Railroad allowed Harrisburg to develop into one of the most industrialized cities in the Northeastern United States. In the mid- to late 20th century, the city's economic fortunes fluctuated with its major industries consisting of government, heavy manufacturing, agriculture, and food services. These economic fluctuations contributed to Harrisburg experiencing a decline of nearly half its population between 1950 and 2000. However, the region is seen as financially stable in part due to the high concentration of state and federal government agencies. The Pennsylvania Farm Show, the largest indoor agriculture exposition in the U.S., was first held in Harrisburg in 1917 and has been held there every early to mid-January since. The city also hosts the annual Great American Outdoor Show, the largest of its kind in the world, among many other events. Harrisburg experienced the Three Mile Island accident on March 28, 1979, in nearby Middletown.