Millersburg is a city in Iowa County, Iowa, United States. The population was 135 at the time of the 2020 census. Millersburg was platted in 18…Millersburg is a city in Iowa County, Iowa, United States. The population was 135 at the time of the 2020 census. Millersburg was platted in 1852. It was named for its founder, Reuben Miller. Millersburg is located at 41°34′22″N 92°9′34″W / 41.57278°N 92.15944°W.