Northrop is a city in Martin County, Minnesota, United States. The population was 223 at the 2020 census. Northrop was platted in 1899…Northrop is a city in Martin County, Minnesota, United States. The population was 223 at the 2020 census. Northrop was platted in 1899. It was named for Cyrus Northrop, president of the University of Minnesota. A post office was established at Northrop in 1900, and remained in operation until it was discontinued in 1972.