In 2002, the National Park Service and the Massachusetts Department of Environmental Management purchased a conservation restriction for Thompson Island. With the assistance of The Trust for Public Land, who helped negotiate the deal, future development was limited to only the existing school campus. It also guaranteed permanent public access to the island, completing the permanent protection of all of the Boston Harbor Islands. Representative Joseph Moakely was instrumental in raising the $2 million of funding appropriated by Congress, and another $2 million matched by Massachusetts.