Aberdeen (ăbˈərdēnˌ) [key]. 1 Town (1990 pop. 13,087), Harford co., NE Md., in a farm region; inc. 1892. Just south, on Chesapeake Bay, is the U.S. army's huge Aberdeen Proving Ground, a major research, development, and testing installation and site of the army ordnance center and school. An ordnance museum is on the grounds. 2 City (1990 pop. 24,927), seat of Brown co., NE S.Dak.; inc. 1882. The trade and distribution center for a wheat and livestock region, it has grain elevators and soybean oil, candy, and dairy-processing plants. Other industries include machinery, electronic and medical equipment, chemicals, computers, printing, wood products, and ethanol. Northern State Univ. and the Dakota Prairie Museum are there. 3 City (1990 pop. 16,565), Grays Harbor co., W Wash., a port of entry on Grays Harbor, at the confluence of the Chehalis and the Wishkah rivers; inc. 1890. With its adjacent twin city, Hoquiam, it has lumbering, shipping, boatbuilding, seafood-processing, and steel and copper foundries. Wood products and lumbering, long the local economic mainstays, have declined since the late 20th cent. The cities serve as a gateway to Olympic National Park (see under Olympic Mts.). Aberdeen is the home port of Washington's tall ship Ambassador Lady Washington.