Middletown is a city located in Butler and Warren counties in the southwestern part of the U.S. state of Ohio, about 35 miles (47 km) north of Cincinnati. Formerly in Lemon, Turtlecreek, and Franklin townships, Middletown was incorporated by the Ohio General Assembly on February 11, 1833, and became a city in 1886.
The population of Middletown as of the 2010 census was 48,694. It is a major city in the Cincinnati-Middletown, OH–KY–IN Metropolitan Statistical Area as defined by the U.S. Census Bureau.
The city was the home of AK Steel Holding Corporation (formerly Armco), a major steel works founded in 1900. Although offices were moved to nearby West Chester Township in 2007, the AK Steel factory is still in Middletown. Middletown is also home to Hook Field Municipal Airport (airport code MWO), which was formerly served by commercial airlines but is currently only for general aviation. A regional campus of Miami University is located in Middletown. In 1957, Middletown was designated as an All-America City.
The city's name is believed to have been given by its founder, Stephen Vail, but questions remain unanswered as to why. One local historian stated that the city received its name because Vail had come from Middletown, New Jersey. Another writer believed that the city was named Middletown because it was the midway point of navigation on the Great Miami River, which was then considered a navigable stream.