West Chester, borough (1990 pop. 18,041), seat of Chester co., SE Pa., W of Philadelphia; inc. 1799. Primarily residential, West Chester was long the trade and processing center for an agricultural region that is now mainly suburbs. Pharmaceuticals and high-technology products are among the borough's diversified manufactures. West Chester Univ. of Pennsylvania is located there. Brandywine Battlefield State Park, on the site of the battle of Brandywine (1777), is nearby. The Turk's Head Inn (1747), an early stagecoach stop, still stands.