Federal Land Ownership: Acquisition and Disposal Authorities [Updated March 26, 2019] [open pdf - 1MB]
From the Document: "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."
CRS Report for Congress, RL34273
Congressional Research Service: https://crsreports.congress.gov/