Shortly after the death of Theodore Roosevelt on January 6, 1919, there were proposals to establish a memorial in his honor. Sylvane Ferris, friend and business associate of Roosevelt during his cattle ranching days in the Dakota Badlands, appointed a committee to pick a site; Medora, North Dakota was selected.
The Little Missouri Badlands were explored in 1924 to outline an area for a Roosevelt National Park. Various plans were proposed, and in 1934 a cooperative agreement to start a Roosevelt Regional Park Project was signed by the Resettlement Administration, the Civilian Conservation Corps (CCC), National Park Service and the State of North Dakota. The federal government wanted the project to become a state park.
The CCC operations began immediately and were administered by National Park Service employees. The North and South Roosevelt Regional Parks had their own camps. By 1935, these sites were designated the Roosevelt Recreation Demonstration Area (RDA). All projects ended in 1941, and North Dakota's state government announced it did not want the land as a state park. Approval was obtained in 1942 to retain the RDA for the purpose of study for possible inclusion into the National Park System. North Dakota Representative William Lemke led the fight to establish a national park, and in 1946, the RDA was officially transferred to the United States Fish and Wildlife Service.
On April 25, 1947, President Truman signed the bill that created Theodore Roosevelt National Memorial Park. The North Unit was added on June 12, 1948. Additional boundary revisions were made in later years. On November 10, 1978, President Carter signed Public Law 95-625 to give the area national park status, now known as Theodore Roosevelt National Park.