Marble Rock is a city in Floyd County, Iowa, United States, along the Shell Rock River. The population was 271 at the time of the 2020 census. Marble Rock has a city park, historical museums, a powerhouse on the river, and a veterans’ memorial. The Marble Rock Historical Society has a website with information about the museums.
Marble Rock is located at 42°57′53″N92°52′4″W (42.964695, -92.867786). Its name derives from the presence of white limestone in the area. The Shell Rock River runs through the west side of town and is available for fishermen and small watercraft. There is a portage around the dam, on the west side of the river, for canoes.
According to the United States Census Bureau, the city has a total area of 0.87 square miles (2.25 km2), of which 0.83 square miles (2.15 km2) is land and 0.04 square miles (0.10 km2) is water.