Groton was established in 1705 when it separated from New London, Connecticut. The town was named after Groton, Suffolk in England. A hundred years before it was established, the Niantic people settled in the area between the Thames River and Pawcatuck River, but they eventually settled in Westerly, Rhode Island. The newcomers to the land were the Pequots, a branch of the Mohawk people who moved eastward into the Connecticut River Valley.

The summer of 1614 was the first time that the Pequots encountered white settlers. They started trading furs for the settlers’ goods, such as steel knives, needles, and boots. In 1633, the Dutch bought land from them and opened a fur trading post. Meanwhile, the English bought land for settlement from the local tribes. The Dutch had unintentionally killed the Pequots’ chief, and this prompted revenge by the Pequot tribe, and this escalated into the Pequot War (1636–38). On the night of May 26, 1637, the Colonial forces arrived outside the Pequot village near the Mystic River. The palisade surrounding the village had only two exits, and their leader Colonel John Mason gave the order to set the village on fire and block off the exits. Those who tried climbing over the palisade were shot; anyone who succeeded in getting over was killed by the Narragansett forces.