New Castle is a city in and the county seat of Lawrence County, Pennsylvania, United States, 50 miles (80 km) northwest of Pittsburgh and near the Pennsylvania–Ohio border just 18 miles (29 km) east 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.
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 the Neshannock Creek, at that time a part of Allegheny County. The Indian town of Kuskusky was listed on early maps in this location . Claiming the land for himself, he laid out what was to become the town of New Castle. Stewart laid out the town of New Castle in April 1798. It comprised approximately that same 50 acres (20 ha), in what was then part of Allegheny County.
In 1825, New Castle became a borough, having a population of about 300.