Middletown, Ohio, a city in Butler County. It is on the Miami River, 29 miles (47 km) north-northeast of Cincinnati and 20 miles (32 km) southwest of Dayton. Armco Steel Corporation, among the world's largest producers of specialized sheet steel, has its main plants here. Other firms make paper and paper products, airplane parts, and machine tools. There are immense natural-gas storage caverns in the area.
Middletown was settled in 1791 and incorporated as a city in 1833. A monument marks the spot where ceremonies in 1825 opened construction on the Miami and Erie Canal, which was in service until 1929.
Population: 51,605.
