Marble Rock is a city in Floyd County, Iowa, United States, along the Shell Rock River. The population was 307 at the 2010 census. On July 24, 2014, Marble Rock will host 10,000+ RAGBRAI riders with ribs, chicken, pie, a beer garden and music from the Chocolate Crackers. Information for RAGBRAI riders is noted below.[1] You can also find photos of MarbleRockIA on Facebook, including the large and shady City Park, the historical museums, the powerhouse on the river, and the veterans' memorial. The Marble Rock Historical Society has a website with information about the museums.