I 1.1: Department of the Interior (1849- )
I 14.1: Census Office (1902-1903)
I 15.1: Division of Public Documents (1869-1895)
I 16.1: Office of Education (1929-1939)
I 17.1: Geographical and Geological Survey of the Rocky Mountain Region (1874- 1879)
I 18.1: Geological and Geographical Survey of the Territories (1872- 1879)
I 19.1: Geological Survey (1879- )
I 19.202: Ecosystem Mission Area (1996- )
I 20.1: Bureau of Indian Affairs (1947- )
I 21.1: General Land Office (1849-1946)
I 22.1: U.S. Department of the Interior Library (1849- )
I 23.1: Patent Office (1849-1925)
I 24.1: Bureau of Pensions (1849-1930)
I 25.1: Commissioner of Railroads (1878-1904)
I 26.1: Entomological Commission (1877-1880)
I 27.1: Bureau of Reclamation (1907- )
I 28.1: Bureau of Mines (1910-1925, 1934-1996)
I 29.1: National Park Service (1916- )
I 30.1: Soil Erosion Service (1933-1935)
I 31.1: Division of Subsistence Homesteads (1933-1935)
I 32.1: Petroleum Administrative Board (1933-1935)
I 33.1: Board on Geographic Names (1934- )
I 34.1: National Bituminous Coal Commission (1935-1939)
I 35.1: Office of Territories (1950-1971)
I 36.1: Puerto Rico Reconstruction Administration (1935-1955)
I 37.1: Motion Pictures Division (1935-1939)
I 38.1: Grazing Service (1939-1946)
I 39.1: Office of Consumers’ Counsel (1935-1939)
I 40.1: Housing Authority (1937-1939)
I 43.1: Information Division (1938-1945)
I 44.1: Bonneville Power Administration (1937-1977)
I 45.1: Bureau of Fisheries (1939-1940)
I 46.1: Bituminous Coal Division (1939-1943)
I 47.1: Bureau of Biological Survey (1939-1940)
I 48.1: Solicitor (1941-?)
I 48.51: Consumers’ Counsel Division (1939-1941)
I 49.1: Fish and Wildlife Service (1940- )
I 50.1: Office of the Petroleum Coordinator for War (1942)
I 51.1: Solid Fuels Administration for War (1943-1947)
I 52.1: War Relocation Authority (1944-1946)
I 53.1: Bureau of Land Management (1946- )
I 54.1: Defense Fisheries Administration (1950-1953)
I 55.1: Office of Minerals Exploration (1958-1965)
I 56.1: Defense Electric Power Administration (1951-1953)
I 57.1: Defense Solid Fuels Administration (1950-1954)
I 58.1: Petroleum Administration for Defense (1950-1954)
I 59.1: Southwestern Power Administration (1943-1977)
I 60.1: Office of Minerals and Solid Fuels (1962-1971)
I 61.1: Oil Import Administration (1959-1971)
I 62.1: Oil Import Appeals Board (1959-1971)
I 63.1: Office of Coal Research (1960-1974)
I 64.1: Office of Oil and Gas (1946-1974)
I 65.1: Southeastern Power Administration (1950-1977)
I 66.1: Bureau of Outdoor Recreation (1963-1978)
I 67.1: Federal Water Quality Administration (1970)
I 68.1: Alaska Power Administration (1967-1977)
I 69.1: Mining Enforcement and Safety Administration (1973- 1978)
I 70.1: Heritage Conservation and Recreation Service (1978- 1981)
I 71.1: Office of Surface Mining Reclamation and Enforcement (1977- )
I 72.1: Bureau of Ocean Energy Management, Bureau of Safety and Environmental Enforcement (1982- )
I 73.2: National Biological Service (1993-1996)
I 74.2: Upper Midwest Environmental Sciences Center (2003- )