Middletown is a borough in Dauphin County, Pennsylvania, United States, on the Susquehanna River, 10 miles (16 km) southeast of Harrisburg. As of the 2010 census it had a population of 8,901. It is part of the Harrisburg–Carlisle Metropolitan Statistical Area.
Middletown was founded in 1755 and was incorporated as a borough in 1828. It was named from its location halfway between Lancaster and Carlisle. It is the oldest incorporated community in Dauphin County and is located within a rich agricultural area forming the western edge of Pennsylvania Dutch Country.Because the town is old, diverse historic architectural styles abound. Middletown has everything from log houses (some whose construction is obscured by modern siding) to Victorian mansions, and beyond. The Simon Cameron House and Bank, B'nai Jacob Synagogue, St. Peter's Kierch, Charles and Joseph Raymond Houses, Henry Smith Farm, and Swatara Ferry House are listed on the National Register of Historic Places.