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.