"The federal government owns roughly 640 million acres, heavily concentrated in 12 western states. Four agencies--the National Park Service (NPS), Fish and Wildlife Service (FWS), and Bureau of Land Management (BLM), in the Department of the Interior, and the U.S. Forest Service (FS) in the Department of Agriculture--administer about 95% of those lands. The extent to which these four federal agencies have authority to acquire and dispose of land varies considerably. The BLM has relatively broad authority for both acquisitions and disposals under the Federal Land Policy and Management Act of 1976. The agency has other authorities for disposing of land, including a law that allows transfers to governmental units and other entities for public purposes. By contrast, the NPS has no general authority to acquire land to create new park units or to dispose of park lands. The FS authority to acquire lands is mostly limited to lands within or contiguous to the boundaries of a national forest. The agency has various authorities to dispose of land, but they are relatively constrained and infrequently used. The FWS has various authorities to acquire lands, but no general authority to dispose of its lands. The agency frequently uses acquisition authority under the Migratory Bird Treaty Act of 1929, because of the availability of funding through the Migratory Bird Conservation Fund."
CRS Report for Congress, RL34273