Chester County is a county located in the U.S. state of Pennsylvania. As of the 2010 census, the population was 498,886. The county seat is West Chester. Chester County was one of the three original Pennsylvania counties created by William Penn in 1682. It was named for Chester, England.
Chester County is included in the Philadelphia-Camden-Wilmington, PA-NJ-DE-MD Metropolitan Statistical Area, as well as the much larger Philadelphia-Reading-Camden, PA-NJ-DE-MD Combined Statistical Area. Eastern Chester County is home to many communities that comprise part of the Main Line western suburbs of Philadelphia, while part of its southernmost portion is considered suburban Wilmington, along with southwest Delaware County.
Chester County is the highest-income county in Pennsylvania and 24th highest in the nation as measured by median household income (as of 2010).