Expanded in 2009, the Refuge includes 410,184 acres, of which 531 acres are terrestrial and 409,653 acres are submerged. Except for a shallow reef surrounding the island, most of the submerged habitat is deep and relatively unexplored.
On January 6, 2009, the Pacific Remote Islands Marine National Monument was established, which includes Baker Island National Wildlife Refuge within its boundaries.
Baker Island is the crest of an ancient steep-sided coral reef cap and massive underlying extinct volcano emerging from the deep ocean floor of the equatorial Pacific. The equatorial undercurrent deflects off the western flank of the seamount, pushing nutrient-rich waters up into the sunlit zone, thereby increasing marine productivity and benefiting many species of marine life. This important phenomenon may be limited only to Howland, Baker, Jarvis Islands, and a few other islands in the Pacific because of their steepness and location on the equator.
The island is uninhabited, and entry is by permit only. U.S. Fish and Wildlife Service personnel visit Baker about every 2 years, though occasionally scientists and researchers team up to share transportation costs to the island more frequently. From Honolulu, it is only accessible by an 8-day ship voyage.