New Castle is the county seat of Lawrence County, Pennsylvania, United States. It is 50 miles (80 km) northwest of Pittsburgh, and near the Pennsylvania–Ohio border, just 18 miles (29 km) southeast of Youngstown, Ohio. The population was 23,128 as of the 2010 census. It is the commercial center of a fertile agricultural region.
New Castle is the principal city of the New Castle, PA Micropolitan Statistical Area, which had a population of 91,108 in 2010. New Castle also anchors the northwestern part of the Pittsburgh-New Castle-Weirton, PA-WV-OH Combined Statistical Area.
As of 2019 U.S. Census estimates, the city had a population of 21,618. This is an approximate decline of 1,476 residents since the 2010 U.S. Census.
In 1798, John Carlysle Stewart, a civil engineer, traveled to western Pennsylvania to resurvey the "donation lands", which had been reserved for veterans of the Revolutionary War. He discovered that the original survey had neglected to stake out approximately 50 acres (20 ha) at the confluence of the Shenango River and Neshannock Creek, at that time a part of Allegheny County. The Indian town of Kuskusky was listed on early maps in this location.