The United States Congress designated the island Saint Croix Island National Monument in 1949. The monument was listed on the National Register of Historic Places on October 15, 1966. It was given its current International Historic Site designation by Congress on September 25, 1984, unique in the national park systems of both the United States and Canada. Since 1968, the island has been managed by the National Park Service from offices at Acadia National Park, the nearest staffed U.S. national park unit, in consultation with Parks Canada, which maintains a viewing and interpretation site on the New Brunswick side of the river.