Westport, so named because it was the westernmost port in the Massachusetts Bay Colony, which was first settled in 1670 as part of the town of Dartmouth by members of the Sisson family. The river, and the land around it, was called “Coaksett” in the original deed: the name, now spelled “Acoaxet,” lives on in the southwestern community along the western branch of the Westport River. Like many areas in the region, Westport was affected by invading Wampanoag Indians during King Philip’s war. Several small mills were built along the Westport River, and in 1787 the town, along with the town of New Bedford, seceded from Dartmouth.

There were several cotton mills along the river, the largest of which was at the junction of the river with Lake Noquochoke on the Dartmouth town line. The Macomber turnip traces its ancestry to turnips sowed in Westport shortly after 1876. During World War II, a coastal defense installation was raised on Gooseberry Island. The town is now mostly residential with a large farming community. Horseneck Beach State Reservation, located to the north and west of Gooseberry Island, is a popular summer destination for many in the area.

There are several unofficial localities within the town: the most prominent of these are Acoaxet, Head of Westport, South Westport, Westport Point, Central Village, and Westport Factory. Acoaxet is unique among them in that because of the west branch of the Westport River, it is inaccessible by land except by passing through neighboring Adamsville, Rhode Island. Westport is approximately 30 miles (48 km) southeast of Providence, Rhode Island, and approximately 60 miles (97 km) south of Boston.