Allegany County is a county in the U.S. state of New York. As of the 2020 census, the population was 46,456. Its county seat is Belmont. Its name derives from a Lenape word, applied by European-American settlers of Western New York State to a trail that followed the Allegheny River; they also named the county after this. The county is part of the Western New York region of the state.
The county is bisected by the Genesee River, flowing north to its mouth on Lake Ontario. During the mid-nineteenth century, the Genesee Valley Canal was built to link southern markets to the Great Lakes and Mohawk River. The county was also served by railroads, which soon superseded the canals in their capacity for carrying freight. Part of the Oil Springs Reservation, controlled by the Seneca Nation, is located in the county.
