Hagerstown (hāˈgərztounˌ) [key], city (1990 pop. 35,445), seat of Washington co., NW Md., on Antietam Creek near its junction with the Potomac River, in the fertile Cumberland Valley; inc. 1791. The city is a shipping and processing center for agricultural products. Its diverse manufactures include pipe organs, aircraft, and furniture. The Hager house (1737), home of the town's founder, is open to the public. The numerous historic sites in the area include the Antietam National Battlefield and Cemetery (see National Parks and Monuments, table) and Fort Frederick (1756).