The Plymouth Historic District encompasses a cluster of five civic buildings (of which four contribute to the district's significance) and the town common of Plymouth, New Hampshire. The buildings are arrayed on the west side of Plymouth's town common, laid out not long after the town's settlement in 1763. The 2-acre (0.81 ha) district includes the town hall/court house, the Pemigewasset National Bank building, and the US Post Office building, as well as the Old Grafton County Courthouse (now a local history museum). The Plymouth Congregation Church also falls within the district bounds, but is not considered contributing. The district was listed on the National Register of Historic Places in 1986.