The Occoquan Bay National Wildlife Refuge is a National Wildlife Refuge located where the Occoquan River meets the Potomac River in Woodbridge, Virginia, United States. The 644-acre (2.61 km2) site, about half of which is wetlands, was used for military research by the U.S. Army's Harry Diamond Laboratories from the 1960s to the 1990s, prior to which (until the 1940s) it was a popular tourist spot, known as Dawson Beach . When the land was purchased from the military, it was temporarily called the Marumsco National Wildlife Refuge. The refuge was formally established and renamed in 1998, and is now run by the United States Fish and Wildlife Service as part of the Potomac River National Wildlife Refuge Complex.