Niagara Falls is a city in Niagara County, New York, United States. As of the 2020 census, the city had a total population of 48,671. It is adjace…Niagara Falls is a city in Niagara County, New York, United States. As of the 2020 census, the city had a total population of 48,671. It is adjacent to the Niagara River, across from the city of Niagara Falls, Ontario, and named after the famed Niagara Falls which they share. The city is within the Buffalo–Niagara Falls metropolitan area and the Western New York region.