| Name | Mark | System [a] | From | To | Successor | Notes |
|---|
| Argentine Central Railway | | | 1905 | 1912 | Argentine and Gray's Peak Railway |
| Argentine and Gray's Peak Railway | | | 1913 | 1918 | N/A |
| Arkansas Valley Railroad | | ATSF | 1900 | 1907 | Atchison, Topeka and Santa Fe Railway |
| Aspen Short Line Railway | | | 1888 | 1893 | Colorado Midland Railroad |
| Aspen and Western Railway | | | 1880 | 1892 | Crystal River Railway |
| Associated Railroads | none | AT&SF, CB&Q (BN), CRI&P, C&S (BN) and D&RGW | 1953 | 1988 | Regional Transportation District | Consortium formed to operate former Denver and Inter-Mountain Railroad line to the Denver Federal Center. Service provided alternately by C&S (BN) and D&RGW on behalf of the other owning railroads. |
| Atchison, Topeka and Santa Fe Railroad | | ATSF | 1873 | 1895 | Atchison, Topeka and Santa Fe Railway |
| Atchison, Topeka and Santa Fe Railway | ATSF | ATSF | 1895 | 1996 | Burlington Northern and Santa Fe Railway |
| Beaver, Penrose and Northern Railway | | | 1909 | 1920 | N/A |
| Book Cliff Railroad | | | 1899 | 1925 | N/A |
| Burlington and Colorado Railroad | | CB&Q | 1881 | 1908 | Chicago, Burlington and Quincy Railroad |
| Burlington Northern Inc. | BN | | 1970 | 1981 | Burlington Northern Railroad |
| Burlington Northern Railroad | BN | | 1981 | 1996 | Burlington Northern and Santa Fe Railway |
| Busk Tunnel Railway | | | 1890 | 1900 | Colorado Midland Railway |
| Cadillac and Lake City Railway | CLK | | 1981 | 1989 | N/A |
| Canon de Agua Railroad | | CB&Q | 1889 | 1890 | Union Pacific, Denver and Gulf Railway |
| Canon City and Cripple Creek Railroad | | | 1897 | 1915 | N/A |
| Canon City and San Juan Railway | | ATSF | 1877 | 1878 | Pueblo and Arkansas Valley Railroad |
| Canon Coal Railway | | DRGW | 1872 | 1878 | Denver and Rio Grande Railway |
| Central Kansas Railway | CKRY | | 1997 | 2001 | Kansas and Oklahoma Railroad |
| Chicago, Burlington and Quincy Railroad | CB&Q | CB&Q | 1881 | 1970 | Burlington Northern Inc. |
| Chicago, Burlington and Quincy Railway | | CB&Q | 1901 | 1907 | N/A | Leased the Chicago, Burlington and Quincy Railroad |
| Chicago, Kansas and Nebraska Railway | | RI | 1888 | 1891 | Chicago, Rock Island and Pacific Railway |
| Chicago, Rock Island and Colorado Railway | | RI | 1888 | 1888 | Chicago, Kansas and Nebraska Railway |
| Chicago, Rock Island and Pacific Railroad | RI, ROCK | RI | 1947 | 1980 | Cadillac and Lake City Railway |
| Chicago, Rock Island and Pacific Railway | RI | RI | 1888 | 1948 | Chicago, Rock Island and Pacific Railroad |
| Chicosa Canon Railway | | CB&Q | 1889 | 1890 | Union Pacific, Denver and Gulf Railway |
| Clear Creek and Guy Gulch Wagon Road Company | | CB&Q | 1871 | 1873 | Colorado Central Railroad |
| Colorado Railroad | | | 1938 | 1957 | N/A |
| Colorado Railroad | | CB&Q | 1906 | 1930 | Colorado and Southern Railway |
| Colorado Railway | | DRGW | 1883 | 1888 | Denver and Rio Grande Railroad |
| Colorado Central Railroad | | CB&Q | 1869 | 1890 | Union Pacific, Denver and Gulf Railway |
| Colorado Central and Pacific Railroad | | CB&Q | 1866 | 1869 | Colorado Central Railroad |
| Colorado and Clear Creek Railroad | | CB&Q | 1865 | 1866 | Colorado Central and Pacific Railroad |
| Colorado Eastern Railroad | | | 1894 | 1915 | N/A |
| Colorado Eastern Railway | | | 1888 | 1894 | Colorado Eastern Railroad |
| Colorado–Kansas Railway | | | 1911 | 1932 | Colorado Railroad |
| Colorado, Kansas and Pacific Railway | CKP | | 2000 | 2003 | Towner Railway |
| Colorado Midland Railroad | CM | | 1917 | 1921 | Midland Terminal Railway |
| Colorado Midland Railroad | | | 1893 | 1897 | Colorado Midland Railway |
| Colorado Midland Railway | | | 1897 | 1917 | Colorado Midland Railroad |
| Colorado Midland Railway | | | 1883 | 1893 | Colorado Midland Railroad |
| Colorado and New Mexico Railroad | | ATSF | 1873 | 1875 | Pueblo and Arkansas Valley Railroad |
| Colorado Northern Railway | | CB&Q | 1883 | 1884 | Denver, Utah and Pacific Railroad |
| Colorado and Northwestern Railroad | | | 1904 | 1909 | Denver, Boulder and Western Railroad |
| Colorado and Northwestern Railway | | | 1897 | 1904 | Colorado and Northwestern Railroad |
| Colorado and Pacific Wagon, Telegraph and Railroad Company | | CB&Q | 1861 | 1871 | Clear Creek and Guy Gulch Wagon Road Company |
| Colorado and Salt Lake Railroad | | CB&Q | 1871 | 1872 | Colorado Central Railroad |
| Colorado and Southeastern Railroad | C&SE | | 1909 | 1952 | N/A |
| Colorado and Southeastern Railway | | | 1903 | 1909 | Colorado and Southeastern Railroad |
| Colorado and Southern Railway | C&S, CS | CB&Q | 1898 | 1981 | Burlington Northern Railroad |
| Colorado Southwestern Railway | | DRGW | 1888 | 1889 | Rio Grande Junction Railway |
| Colorado Springs and Cripple Creek District Railway | CCD | | 1899 | 1920 | N/A |
| Colorado and Utah Railway | | | 1886 | 1892 | Crystal River Railway |
| Colorado and Wyoming Railroad | | CB&Q | 1887 | 1908 | Chicago, Burlington and Quincy Railroad |
| Colorado, Wyoming and Eastern Railway | | UP | 1914 | 1924 | Northern Colorado and Eastern Railroad |
| Colorado, Wyoming and Great Northern Railroad | | | 1894 | 1899 | Book Cliff Railroad |
| Cripple Creek and Colorado Springs Railroad | | | 1915 | 1921 | Midland Terminal Railway |
| Cripple Creek District Railway | | | 1897 | 1899 | Colorado Springs and Cripple Creek District Railway |
| Crystal River Railroad | | | 1898 | 1941 | N/A |
| Crystal River Railway | | | 1892 | 1898 | Crystal River Railroad |
| Crystal River and San Juan Railroad | | | 1906 | 1941 | N/A |
| Denver Railroad and Land Company | | | 1886 | 1887 | Denver Railroad, Land and Coal Company |
| Denver Railroad, Land and Coal Company | | | 1887 | 1888 | Colorado Eastern Railway |
| Denver Railway | DRWY | | 1989 | 1993 | Denver Rock Island Railroad |
| Denver and Boulder Valley Railroad | | UP | 1870 | 1898 | Union Pacific Railroad |
| Denver, Boulder and Western Railroad | | | 1909 | 1919 | N/A |
| Denver Circle Railroad | | ATSF | 1880 | 1886 | Denver and Santa Fe Railway |
| Denver, Clear Creek and Western Railway | | DRGW | 1888 | 1899 | Denver and Rio Grande Railroad |
| Denver, Cripple Creek and Southwestern Railroad | | CB&Q | 1896 | 1899 | Colorado and Southern Railway |
| Denver, Golden and Salt Lake Railroad | | CB&Q | 1881 | 1917 | Chicago, Burlington and Quincy Railroad |
| Denver and Inter-Mountain Railroad | D&IM, DIM | | 1909 | 1953 | Associated Railroads (AT&SF, CB&Q, CRI&P, C&S and D&RGW) | Electric after 1909 |
| Denver and Inter-Mountain Railway | | | 1904 | 1909 | Denver and Inter-Mountain Railroad |
| Denver, Lakewood and Golden Railroad | | | 1890 | 1904 | Denver and Inter-Mountain Railway |
| Denver, Laramie and Northern Railroad | | | 1917 | 1917 | Great Western Railway of Colorado |
| Denver, Laramie and Northwestern Railroad | | | 1910 | 1917 | Denver, Laramie and Northern Railroad |
| Denver, Laramie and Northwestern Railway | | | 1906 | 1910 | Denver, Laramie and Northwestern Railroad |
| Denver, Leadville and Gunnison Railway | | CB&Q | 1889 | 1898 | Colorado and Southern Railway |
| Denver, Longmont and Northwestern Railroad | | CB&Q | 1881 | 1883 | Colorado Northern Railway |
| Denver, Marshall and Boulder Railway | | CB&Q | 1885 | 1890 | Union Pacific, Denver and Gulf Railway |
| Denver and Middle Park Railroad | | CB&Q | 1883 | 1890 | Union Pacific, Denver and Gulf Railway |
| Denver and Montana Railroad | | CB&Q | 1899 | 1908 | Chicago, Burlington and Quincy Railroad |
| Denver and New Orleans Railroad | | CB&Q | 1881 | 1886 | Denver, Texas and Gulf Railroad |
| Denver, Northwestern and Pacific Railway | | DRGW | 1902 | 1913 | Denver and Salt Lake Railroad |
| Denver Pacific Railway and Telegraph Company | | UP | 1867 | 1880 | Union Pacific Railway |
| Denver and Rio Grande Railroad | | DRGW | 1886 | 1921 | Denver and Rio Grande Western Railroad |
| Denver and Rio Grande Railway | | DRGW | 1870 | 1886 | Denver and Rio Grande Railroad |
| Denver and Rio Grande Western Railroad | D&RG, D&RGW, DRGW | DRGW | 1920 | 1997 | Union Pacific Railroad |
| Denver and Salt Lake Railroad | D&SL | DRGW | 1912 | 1927 | Denver and Salt Lake Railway |
| Denver and Salt Lake Railway | D&SL | DRGW | 1926 | 1947 | Denver and Rio Grande Western Railroad |
| Denver and Salt Lake Western Railroad | | DRGW | 1924 | 1947 | Denver and Rio Grande Western Railroad |
| Denver and Santa Fe Railway | | ATSF | 1887 | 1900 | Atchison, Topeka and Santa Fe Railway |
| Denver, South Park and Hill Top Railway | | CB&Q | 1896 | 1897 | Denver, Leadville and Gunnison Railway |
| Denver, South Park and Pacific Railroad | | CB&Q | 1873 | 1889 | Denver, Leadville and Gunnison Railway |
| Denver, South Park and Pacific Railway | | CB&Q | 1872 | 1873 | Denver, South Park and Pacific Railroad |
| Denver and Southwestern Railway | | | 1899 | 1904 | Cripple Creek Central Railway (holding company) |
| Denver Terminal Railroad | DTMR | | 1986 | 1989 | Denver Railway |
| Denver, Texas and Gulf Railroad | | CB&Q | 1885 | 1890 | Union Pacific, Denver and Gulf Railway |
| Denver, Texas and Fort Worth Railroad | | CB&Q | 1887 | 1890 | Union Pacific, Denver and Gulf Railway |
| Denver Union Railway and Terminal Company | | UP | 1889 | 1900 | Union Pacific Railroad |
| Denver Union Terminal Railway | DUT | ATSF/ CB&Q/ DRGW/ RI/ UP | 1912 | 2001 | Regional Transportation District |
| Denver, Utah and Pacific Railroad | | CB&Q | 1880 | 1908 | Chicago, Burlington and Quincy Railroad |
| Denver, Western and Pacific Railway | | CB&Q | 1880 | 1885 | Denver, Marshall and Boulder Railway |
| Elk Mountain Railway | | | 1887 | 1898 | Crystal River Railroad |
| Florence and Cripple Creek Railroad | | | 1893 | 1915 | Cripple Creek and Colorado Springs Railroad |
| Fort Collins Development Railway | | CB&Q | 1902 | 1908 | Colorado Railroad |
| Fort Worth and Denver Railway | FWD | CB&Q | 1881 | 1982 | Burlington Northern Railroad |
| Georgetown, Breckenridge and Leadville Railway | | CB&Q | 1881 | 1890 | Union Pacific, Denver and Gulf Railway |
| Gilpin Railroad | | CB&Q | 1909 | 1917 | N/A |
| Gilpin Tramway Company | | CB&Q | 1886 | 1906 | Gilpin Railroad |
| Golden Circle Railroad | | | 1896 | 1915 | Cripple Creek and Colorado Springs Railroad |
| Golden City and Gilpin County Wagon and Railroad Company | | CB&Q | 1870 | 1872 | Colorado Central Railroad |
| Golden City and South Platte Railway and Telegraph Company | | | 1872 | 1880 | N/A |
| Grand Valley Railway | | DRGW | 1886 | 1887 | Denver and Rio Grande Railroad |
| Greeley, Salt Lake and Pacific Railway | | CB&Q | 1881 | 1890 | Union Pacific, Denver and Gulf Railway |
| Greeley Terminal Railway | | | 1909 | 1917 | N/A |
| Holly and Swink Railway | | ATSF | 1906 | 1907 | Atchison, Topeka and Santa Fe Railway |
| Kansas–Colorado Railroad | | | 1908 | 1910 | Colorado–Kansas Railway |
| Kansas Pacific Railway | | UP | 1869 | 1880 | Union Pacific Railway |
| Laramie, Hahns Peak and Pacific Railway | | UP | 1911 | 1914 | Colorado, Wyoming and Eastern Railway |
| Laramie, North Park and Western Railroad | | UP | 1924 | 1951 | Union Pacific Railroad |
| Larimer and Routt County Railway | | UP | 1907 | 1914 | Colorado, Wyoming and Eastern Railway |
| Leadville Mineral Belt Railway | | CB&Q | 1898 | 1900 | Colorado and Southern Railway |
| Leadville, Ten Mile and Breckenridge Railway | | DRGW | 1880 | 1880 | Denver and Rio Grande Railway |
| Little Book Cliff Railway | | | 1889 | 1894 | Colorado, Wyoming and Great Northern Railroad |
| London, South Park and Leadville Railroad | | | 1882 | 1885 | South Park and Leadville Short Line Railroad |
| Longmont and Erie Railroad | | CB&Q | 1878 | 1881 | Denver, Longmont and Northwestern Railroad |
| Midland Terminal Railway | MTR | | 1892 | 1949 | N/A |
| Missouri Pacific Railroad | MP | MP | 1917 | 1997 | Union Pacific Railroad |
| Missouri Pacific Railway | | MP | 1887 | 1917 | Missouri Pacific Railroad |
| Mount Carbon, Gunnison and Lake City Railroad and Coal Transportation Company | | CB&Q | 1877 | 1881 | Denver, South Park and Pacific Railroad |
| Nebraska, Kansas and Colorado RailNet | NKCR | | 1996 | 2005 | Nebraska Kansas Colorado Railway |
| Northern Colorado and Eastern Railroad | | UP | 1924 | 1924 | Laramie, North Park and Western Railroad |
| Northwestern Terminal Railroad | | DRGW | 1927 | 1968 | Denver and Rio Grande Western Railroad |
| Northwestern Terminal Railway | | DRGW | 1904 | 1927 | Northwestern Terminal Railroad |
| Platt Valley Railway | | | 1993 | 1993 | Denver Rock Island Railroad |
| Pueblo and Arkansas Valley Railroad | | ATSF | 1875 | 1900 | Atchison, Topeka and Santa Fe Railway |
| Pueblo and Salt Lake Railway | | ATSF | 1873 | 1875 | Pueblo and Arkansas Valley Railroad |
| Pueblo and State Line Railroad | | MP | 1887 | 1910 | Missouri Pacific Railway |
| Pueblo Union Depot and Railroad Company | | ATSF/ CB&Q/ DRGW/ MP/ RI | 1887 | | |
| Rio Grande Railroad | | DRGW | 1900 | 1908 | Denver and Rio Grande Railroad |
| Rio Grande Gunnison Railway | | DRGW | 1891 | 1908 | Denver and Rio Grande Railroad |
| Rio Grande Junction Railway | | DRGW | 1889 | 1947 | Denver and Rio Grande Western Railroad |
| Rio Grande, Pagosa and Northern Railroad | | DRGW | 1899 | 1908 | Denver and Rio Grande Railroad |
| Rio Grande and Pagosa Springs Railroad | | | 1895 | 1914 | N/A |
| Rio Grande, Pueblo and Southern Railroad | | DRGW | 1902 | 1908 | Denver and Rio Grande Railroad |
| Rio Grande Sangre de Cristo Railroad | | DRGW | 1901 | 1908 | Denver and Rio Grande Railroad |
| Rio Grande Southern Railroad | | DRGW | 1889 | 1951 | N/A |
| Rio Grande Western Railway | | DRGW | 1889 | 1908 | Denver and Rio Grande Railroad |
| Road Canon Railroad | | CB&Q | 1889 | 1890 | Union Pacific, Denver and Gulf Railway |
| St. Joseph and Iowa Railroad | | RI | 1888 | 1888 | Chicago, Rock Island and Pacific Railway |
| San Luis Southern Railway | | | 1909 | 1928 | San Luis Valley Southern Railway |
| San Luis Valley Southern Railway | | | 1928 | 1953 | Southern San Luis Valley Railroad |
| Silverton Railroad | | | 1887 | 1904 | Silverton Railway |
| Silverton Railway | | | 1904 | 1922 | N/A |
| Silverton, Gladstone and Northerly Railroad | | | 1899 | 1915 | Silverton Northern Railroad |
| Silverton Northern Railroad | | | 1895 | 1941 | N/A |
| South Park and Leadville Short Line Railroad | | | 1885 | 1900 | N/A |
| Southern San Luis Valley Railroad | SSLV | | 1953 | 1996 | N/A |
| State Line and Denver Railway | | DRGW | 1889 | 1889 | Rio Grande Western Railway |
| Trinidad Railway | TRIN | | 1992 | | | Still exists as a joint lessor of the BNSF Railway and Union Pacific Railroad |
| Trinidad and Denver Railroad | | DRGW | 1886 | 1888 | Denver and Rio Grande Railroad |
| Trinidad and Denver Terminal and Railway Company | | DRGW | 1888 | 1899 | Denver and Rio Grande Railroad |
| Uintah Railway | | | 1903 | 1939 | N/A |
| Union Depot and Railroad Company | | ATSF/ CB&Q/ DRGW/ RI/ UP | 1879 | 1899 | Union Depot and Railway Company |
| Union Depot and Railway Company | | ATSF/ CB&Q/ DRGW/ RI/ UP | 1899 | 1914 | Denver Union Terminal Railway |
| Union Pacific Railway | | UP | 1880 | 1898 | Union Pacific Railroad |
| Union Pacific Railway, Eastern Division | | UP | 1866 | 1869 | Kansas Pacific Railway |
| Union Pacific, Denver and Gulf Railway | | CB&Q | 1890 | 1898 | Colorado and Southern Railway |
| Union Pacific, Lincoln and Colorado Railway | | UP | 1888 | 1898 | N/A | Sold at foreclosure; no property in Colorado |
| Walsenburg and Western Railway | | CB&Q | 1907 | 1910 | Colorado Railroad |