Alleghany is a small census-designated place in Sierra County, California state, in the Sierra Nevada mountains. It is situated in the Gold Country and continues to be a significant location for gold mining. The famous 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 (California State Route 49) and consists largely of a single main street. The town is home to a post office, a bar (Casey's Place), and a mining museum. At the 2010 census, the population was 58.
The town is named after the Alleghany Tunnel Mine, which itself is named after Alleghany river.