Rail Road Flat (formerly, Independence Flat and Railroad Flat) is a census-designated place (CDP) in Calaveras County, California, United States. The population was 475 at the 2010 census, down from 549 at the 2000 census.
This historic mining town, elevation 2,600 feet (788 m), was named after primitive mule-drawn ore cars used here. There was never actually a railroad here. The town was established in 1849. It was the site of an Indian council as well as the center of rich placer and quartz mining. Its largest producer was the Petticoat Mine. The post office was established in 1857, closed in 1858, and re-established in 1869 and the Edwin Taylor store built in 1867. The town's population was decimated in 1880 by black fever.
The Clark Reservoir was created when an engineer named W.V. Clark constructed a ditch from the Mokelumne River, as there was not much water to work the placers. The reservoir, located on his property, supplied water to the mines and to the town.
The town is registered as California Historical Landmark #286.