Ralston is a city in Carroll and Greene counties in the U.S. state of Iowa. The population was 81 at the time of the 2020 census. Ralston was i…Ralston is a city in Carroll and Greene counties in the U.S. state of Iowa. The population was 81 at the time of the 2020 census. Ralston was incorporated in 1900. It was named for William Chapman Ralston, a California banker.