Plum Tree Island National Wildlife Refuge is situated on the southwestern corner of the Chesapeake Bay in the City of Poquoson and is strategically located almost midpoint on the Atlantic Flyway. It consists of 3,450 acres of saltmarsh, shrub-scrub and wooded habitats that provide a haven for waterfowl, marsh-birds, and shorebirds. Refuge wetlands include an estimated 1,000 acres of low-lying, tidal salt marsh that flood twice daily. During monthly high tides and storms, an additional 1,500 acres may also flood. Due to its isolation, this area was historically used for stock grazing, hunting, and fishing. It was acquired by the Federal Government for an Aviation Experimental Station in 1917. Air Force records indicate that the area was used as a gunnery and bombing practice range until the latter part of the 1950's. On May 22, 1972, the area was transferred to the Department of the Interior. Attempts to clear the military munitions from the property have only been partially successful; because the nature of the wetlands make it impractical to clear subsurface ordinances. NASA has also used the area as a free flight zone for testing model aircraft until recently. Because of the unexploded ordinance hazard, Plum Tree Island Refuge is closed to the public. It remains an emergency jettison zone for the Air Force.