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historic town, seat (1634) of York county, southeastern Virginia, U.S. It is situated on the south bank of the York River across from Gloucester Point, just east-southeast of Williamsburg. The area around Yorktown was settled in 1630, but the town itself developed after 1691 when a port was authorized by Virginia's General Assembly. Yorktown became a busy shipping centre, and its Colonial Custom House (1706; restored) is regarded as the cradle of the American tariff system. By 1750, however, its commercial role had declined together with the Tidewater Virginia tobacco trade. Yorktown's place in history was assured by the siege and surrender there of British forces under General Lord Cornwallis in 1781, an event that virtually assured an American victory in the American Revolution. During the American Civil War Union forces under General George McClellan defeated General John Magruder's Confederate troops in May 1862 and occupied the town.