Thompson Island is an island in the Boston Harbor, about 1 mile offshore from downtown Boston, Massachusetts. The island is managed by the Thompson Island Outward Bound Education Center, a non-profit education organization. The island is open to visitors on Saturdays and Sundays from Memorial Day through Labor Day; otherwise access is by arrangement only. Thompson Island is one of the largest, most accessible and ecologically diverse islands in the Boston Harbor Islands National Recreation Area.
The island has a size of 170 acres (0.69 km2), and the highest point is a drumlin that reaches a height of 78 feet above sea level. The rest of the island comprises low rolling hills and a salt marsh. The island has a mixed vegetation, including hardwood tree stands, remnant pear and apple orchards, ornamental trees and shrubs, and salt marsh grasses. The island has open meadows, forests, marine wetlands, sumac groves, and a variety of other geological features as well. Amenities include a formal school campus complete with classrooms, dormitories, dining hall, auditoriums, gymnasium, lab space, outdoor challenge courses, and climbing towers. At low tide, a sandbar connects it to Squaw Rock on the Squantum peninsula, allowing land travel between the two.
In 1626, four years before the Puritans arrived, David Thompson established a trading post to trade with the Neponset Indians on the island that now bears his name. Thompson was a Scot who had been superintending the settlement of Sir Ferdinando Gorges and Captain John Mason near Portsmouth, New Hampshire. For the next two centuries, Thompson Island was leased to several families for farming.