Portsmouth, city, seat (1816) of Scioto county, southern Ohio, U.S. Portsmouth lies along the Ohio River at the mouth of the Scioto River, about 90 miles (145 km) south of Columbus. It was founded in 1803 by Maj. Henry Massie, a land speculator, who named the place for Portsmouth, N.H., hometown of Massie’s friend Josiah Shackford. Its early growth was spurred by the opening (1832) of the Ohio and Erie Canal, when it became a point of transfer from canal barges to river packets. With the end of the steamboat era it developed as a railway centre; the first railroad arrived in 1853. Bridges now connect the city to South Portsmouth and Fullerton, in Kentucky. Following disastrous river floods in 1937, a floodwall 77 feet (23 metres) high was built (completed 1948) to protect the city. Between 1992 and 2002 the city decorated the wall with a series of more than 50 murals by artist Robert Dafford depicting scenes from Portsmouth and Scioto county history. The Greenup Locks and Dam complex is 10 miles (16 km) up the Ohio River.
Nearby stone quarries and clay deposits have supplied building materials for many notable structures, including the Canadian Parliament buildings at Ottawa. The city’s diversified manufactures include steel, chemicals, plastics, firebricks, and iron castings. The city is the seat of Shawnee State University (1986). Horseshoe Mound is in the city; Shawnee State Forest and Shawnee State Park are nearby, and portions of Wayne National Forest are to the north and east. The Southern Ohio Museum and Cultural Center displays traveling and permanent exhibitions of American art, including a large collection of paintings by Clarence Carter, a Portsmouth native. The River Days festival and the National Outboard Motor Boat Championship Races are annual events. Inc. town, 1814; city, 1851. Pop. (2000) 20,909; (2010) 20,226.