Alleghany is a small census-designated place in Sierra County, California, United States in the Sierra Nevada. It is situated in the Gold Country and continues to be a significant locale for gold mining. The Sixteen To One Mine has been in operation since the days of the California Gold Rush. The town is 20 miles from the nearest highway and consists largely of a single main street. The town is home to a post office, a bar, and a mining museum. The population was 58 at the 2010 census.