Middletown is a town in Frederick County, Maryland, United States. The population was 4,136 at the 2010 census.
A young Lieutenant George Washington, while surveying the South Mountain area, reported that the valley to the east was one of the most beautiful places he had ever seen. Later, as a Colonel in 1755, he was to accompany General Braddock on the old Indian Trail that ran through the valley on his way to Fort Cumberland. The early German and English settlers started to arrive in the valley in the 1730s. Among them was Michael Jesserong, who paid £66 for 50 acres (200,000 m2). He named his property Middletown and sold the first lots there in 1767, the date officially marked as that of the town’s founding. The history of Middletown is a mirror on the nation’s development. Main Street spread to the west with construction of the National Pike through the town in 1806; the telegraph lines from Frederick to Hagerstown were routed through Middletown in 1854; and in 1896, car 11 of the Frederick Middletown Railway made its first run to Middletown. During the Civil War, both armies passed through the town to the battles of South Mountain and Antietam. In the aftermath of those battles, Middletown opened its churches and homes to care for the wounded.