Chester County, Pennsylvania, is located in the southeastern part of the state, within the Delaware Valley region. It lies about 40 miles west of Philadelphia and 25 miles north of Wilmington, Delaware. The county is part of the Philadelphia-Camden-Wilmington metropolitan area and is known locally as "Chesco"

. The county seat is West Chester, which is centrally located within the county. Chester County borders Maryland and Delaware to the south, and the Schuylkill River to the northeast. It encompasses a mix of hilly piedmont terrain and waterways such as the Brandywine and French creeks

. Historically, Chester County was one of the three original Pennsylvania counties created by William Penn in 1682. The city of Chester, now in neighboring Delaware County, was originally the county seat before it moved to West Chester in 1788

. In summary, Chester County is a historically significant county situated in southeastern Pennsylvania, west of Philadelphia, with West Chester as its administrative center