Lancaster is a town located along the Connecticut River in Coös County, New Hampshire, United States. The town is named after the city of Lancaster in England. As of the 2020 census, the town population was 3,218, the second largest in the county after Berlin. It is the county seat of Coös County and gateway to the Great North Woods Region of the state. Lancaster, which includes the villages of Grange and South Lancaster, is home to Weeks State Park and the Lancaster Fair.