Delaware County is a county located in the U.S. state of Iowa. As of the 2020 census, the population was 17,488. The county seat is Manchester. The county takes its name after the U.S. state of Delaware.

Manchester is a city in Delaware Township and the county seat of Delaware County, Iowa, United States. The population was 5,065 at the time of the 2020 census. Manchester is located at the intersection of U.S. Route 20 and State Highway 13 and is the largest community in Delaware County.