Plymouth is an incorporated borough in Luzerne County, Pennsylvania, United States 4 miles (6 km) west of Wilkes Barre, on the Susquehanna River. Prior to its incorporation in 1866, it was part of Plymouth Township, established in 1769 by the Susquehanna Company and claimed by Connecticut based on the charter of that colony. The Pennamite-Yankee War was fought in the environs. It is situated in the rich hard coal fields of Pennsylvania. Coal was first shipped in 1807. In the past, the chief products of its industrial establishments included mining drilling machines, miners' squibs, silk hosiery, and lumber products. In 1890, Plymouth's population was 9,340; in 1900, it was 13,649. In 1910, 16,996 lived here; in 1920, 16,500; and in 1940, 15,507. The population was 6,507 at the 2000 census.
Plymouth is located at 41°14′31″N 75°56′53″W / 41.241859°N 75.947997°W / 41.241859; -75.947997.
According to the United States Census Bureau, the borough has a total area of 1.2 square miles (3.1 km2), of which, 1.1 square miles (2.8 km2) of it is land and 0.1 square miles (0.3 km2) of it (8.40%) is water.