Pawcatuck is a census-designated place (CDP) in the town of Stonington which is located in New London County, Connecticut, United States. The population was 5,474 at the 2000 census. It is located across the Pawcatuck River from Downtown Westerly in Rhode Island. It includes the Mechanic Street Historic District, which is listed on the National Register of Historic Places. The historic district includes sites of shipbuilding, mills, and worker housing in a 147-acre (0.59 km) area.