Harper is a city in Keokuk County, Iowa, United States. The population was 118 at the time of the 2020 census. According to the United Stat…Harper is a city in Keokuk County, Iowa, United States. The population was 118 at the time of the 2020 census. According to the United States Census Bureau, the city has a total area of 0.09 square miles, all of it land.