The reserve encompasses 2,353 acres of land on Prudence, Patience and Hope islands and 1,591 acres of water adjoining the islands out to a depth of 18 feet. All three islands were used as farmland during the Colonial area. By the 20th century, farming declined and Prudence Island began to attract summer residence. The U.S. military established a presence on the island during World War II and remained until the land was turned over to the state of Rhode Island in 1972. In addition to its human inhabitants, Prudence island supports one of the densest herds of white tailed deer in the northeast. Being very close to the entirely wooded Patience Island, deer can swim between these two islands.