Chester is a city in Delaware County, Pennsylvania, United States, with a population of 33,972 at the 2010 census. Chester is situated on the Delaware River, between the cities of Philadelphia and Wilmington, Delaware.
By 1682, Upland was the most populous town of the new Province of Pennsylvania. On October 27, the ship Welcome arrived at the town, bearing William Penn on his first visit to the province. Penn renamed the settlement for the English city of Chester.
Chester served as the county seat for Chester County, which then stretched from the Delaware River to the Susquehanna River. In 1789, the city became the county seat for the newly created Delaware County (whereupon Chester County became landlocked, with West Chester as its county seat), but the county seat was moved to the borough of Media in 1851. The courthouse is near the new City Hall building.
Chester's naval shipyard supplied the Union during the Civil War, and the United States in subsequent wars until the shipyard at Philadelphia became dominant after World War II. America's largest postbellum shipyard, John Roach's Delaware River Iron Ship Building and Engine Works, was also located at Chester. The Sun Shipbuilding & Drydock Co., later Pennsylvania Shipyard & Dry Dock Company, was located in Chester until it closed in 1990. Two ships of the United States Navy have been named USS Chester in honor of the city.
On April 10, 1917 an explosion at the Eddystone Ammunition Corporation near Chester resulted in the deaths of 133 workers, mostly women.
Chester is one of numerous places that claim to be the birthplace of the hoagie sandwich. It is also known as the "Cradle of Rock 'n Roll" as Bill Haley & His Comets first performed and maintained their headquarters in the Chester area.
The following are listed on the National Register of Historic Places: Delaware County National Bank, 1724 Chester Courthouse, Chester Waterside Station of the Philadelphia Electric Company, Old Main and Chemistry Building, William Penn Landing Site, and the former Second Street Bridge.