Lancaster is a city in and the county seat of Grant County, Wisconsin, United States. The population was 3,907 at the 2020 census. Lancas…Lancaster is a city in and the county seat of Grant County, Wisconsin, United States. The population was 3,907 at the 2020 census. Lancaster originated as a planned community to serve as the county seat for Grant County. Anticipating the county's establishment in 1836, Major Glendower M. Price, a Cassville merchant and land speculator, purchased the site of Lancaster for its central location in the county. Major Price platted the town on a compass-aligned grid in 1837, reserving a large central square for the new county government. He was persuaded to name the city Lancaster by a relative who migrated from Lancaster, Pennsylvania. Maj. Price and Daniel Banfill contracted to construct the first county courthouse, which stood on the square from 1838–1851. A second courthouse was constructed in 1852–1853 and enlarged in 1865. The present, third courthouse was constructed on the site in 1902.