One of the three original counties formed by William Penn in November 1682. It did not become an inland county until 1789. Its name derives from Cheshire (i.e., Chester-shire), England, from which many of its early settlers came. West Chester, the county seat since 1788, was incorporated as a borough on March 28, 1799. It was named for Chester, the older county seat (now in Delaware County), which in turn derived its name from the shire town of Cheshire.

     Quakers were very influential in the early period, and an older Swedish population that pre-dated William Penn’s charter was absorbed. Chester shares with Montgomery County the Valley Forge encampment and with Delaware County the Brandywine Battlefield. Iron works began before the Revolution, followed by production of paper, textiles, and bricks. Accessibility increased with the Lancaster Pike (1795), Schuylkill Navigation Canal (1825), and Columbia Railroad (1840s). In the 1890s the county became a residential location for commuting Philadelphia workers. Chester was an early producer of a valuable mushroom crop, and has long excelled in fruit growing, dairying, livestock breeding, and raising flowers. Thirty percent of the land is farmed. The Pierre du Pont Arboretum and Gardens arose in the nineteenth century. The institute that became Lincoln University was founded in 1854 to educate African Americans, and there were Underground Railroad stations at West Chester, Phoenixville, Oxford, and Kennett Square.