Alliance is a city and the county seat of Box Butte County, in the western part of the state of Nebraska, in the Great Plains region of the United States. Its population was 8,151 at the 2020 census. Alliance is home to Carhenge, a replica of Stonehenge constructed with automobiles, which is located north of the city. It is also the location of Alliance Municipal Airport, the least-used airport in the mainland United States.