Middletown, city, Butler County, southwestern Ohio, on the Great Miami River, near Hamilton; settled 1791, incorporated as a city 1886. Manufactures include steel, paper products, machinery, and aerospace equipment. A junior college is here. The city is the location of an annual hot air balloon contest. Laid out in 1802 and probably named for Middletown, New Jersey, the community was a farm-trade and transportation center in the 19th century and became a steel-making hub about 1900. Population 43,719 (1980); 51,605 (2000).
