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 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.
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