Fort Winthrop was a defensive fortification in Boston Harbor named after John Winthrop, the early governor of the Massachusetts Bay Colony. It was built on Governors Island, which had been granted to Winthrop in 1632. His family owned the island until 1808, when the United States acquired land in the center of the island for the construction of a fort. Between 1808 and 1812 the government built an earthen fort on that land. In 1834 the government acquired the rest of the island, and construction began on a stone fort in the 1840s.