| Name | Mark | System | From | To | Successor | Notes |
| Annapolis and Baltimore Short Line Railroad | | | 1880 | 1894 | Baltimore and Annapolis Short Line Railroad | - |
| Annapolis and Elk Ridge Railroad | | | 1837 | 1885 | Annapolis, Washington and Baltimore Railroad | - |
| Annapolis, Washington and Baltimore Railroad | | | 1886 | 1908 | Washington, Baltimore and Annapolis Electric Railway | - |
| Bachman Valley Railroad | | | 1870 | 1886 | Baltimore and Harrisburg Railway | - |
| Baltimore and Annapolis Railroad | BLA | | 1935 | 1993 | Canton Railroad | - |
| Baltimore and Annapolis Short Line Railroad | | | 1894 | 1921 | Washington, Baltimore and Annapolis Electric Railroad | - |
| Baltimore Belt Railroad | | B&O | 1888 | | | - |
| Baltimore, Carroll and Frederick Railroad | | WM | 1852 | 1853 | Western Maryland Railroad | - |
| Baltimore, Chesapeake and Atlantic Railway | BCA | PRR | 1894 | 1928 | Baltimore and Eastern Railroad | - |
| Baltimore and Cumberland Railway | | | | | | - |
| Baltimore and Cumberland Valley Railway | | WM | 1878 | 1917 | Western Maryland Railway | - |
| Baltimore and Delaware Bay Railroad | | PRR | 1881 | 1902 | Delaware Railroad | - |
| Baltimore and Delta Railway | | | 1878 | 1882 | Maryland Central Railroad | - |
| Baltimore and Eastern Railroad | BE | PRR | 1923 | 1976 | Consolidated Rail Corporation | - |
| Baltimore and Eastern Railroad | | PRR | 1886 | 1894 | Baltimore, Chesapeake and Atlantic Railway | - |
| Baltimore, Hampden and Towsontown Railway | | | 1874 | 1878 | Baltimore and Delta Railway | - |
| Baltimore and Hanover Railroad | | WM | 1877 | 1886 | Baltimore and Harrisburg Railway | - |
| Baltimore and Harrisburg Railway | | WM | 1886 | 1917 | Western Maryland Railway | - |
| Baltimore and Lehigh Railroad | | | 1891 | 1894 | Baltimore and Lehigh Railway | - |
| Baltimore and Lehigh Railway | | | 1894 | 1901 | Maryland and Pennsylvania Railroad | - |
| Baltimore and Ohio Railroad | B&O, BO | B&O | 1827 | 1987 | Chesapeake and Ohio Railway | - |
| Baltimore and Ohio Railroad in Pennsylvania | | B&O | 1912 | 1980 | Baltimore and Ohio Railroad | - |
| Baltimore and Philadelphia Railroad | | PRR | 1852 | 1854 | Philadelphia and Baltimore Central Railroad | - |
| Baltimore and Port Deposit Railroad | | PRR | 1832 | 1838 | Philadelphia, Wilmington and Baltimore Railroad | - |
| Baltimore and Potomac Railroad | | PRR | 1853 | 1902 | Philadelphia, Baltimore and Washington Railroad | - |
| Baltimore and Sparrows Point Railroad | | PRR | 1887 | 1919 | Philadelphia, Baltimore and Washington Railroad | - |
| Baltimore and Susquehanna Railroad | | PRR | 1828 | 1854 | Northern Central Railway | - |
| Baltimore and Swann Lake Passenger Railway | | | 1868 | 1874 | Baltimore, Hampden and Towsontown Railway | - |
| Baltimore, Towsontown, Dulaney's Valley and Delta Narrow Gauge Railway | | | 1876 | 1878 | Baltimore and Delta Railway | - |
| Bay Coast Railroad | BCR | | 2006 | 2018 | Delmarva Central Railroad | - |
| Bay Ridge and Annapolis Railroad | | B&O | 1886 | 1903 | N/A | - |
| Cambridge and Seaford Railroad | | PRR | 1882 | 1899 | Delaware Railroad | - |
| Caton and Loudon Railway | | PRR | 1945 | 1973 | N/A | - |
| Catonsville Short Line Railroad | | PRR | 1882 | 1945 | Caton and Loudon Railway | - |
| Central Railroad of Maryland | | PRR | 1913 | 1914 | York, Hanover and Frederick Railway Company | - |
| Chaffee Railroad | | WM | 1918 | 1950 | Western Maryland Railway | - |
| Chambersburg, Greencastle and Hagerstown Railroad | | PRR | 1853 | 1859 | Franklin Railroad | - |
| Chesapeake Railroad | CHRR | | 1995 | 2000 | N/A | - |
| Chesapeake Beach Railway | | | 1896 | 1935 | East Washington Railway | - |
| Chesapeake and Curtis Bay Railroad | | WM | 1916 | 1989 | CSX Transportation | - |
| Chesapeake and Ohio Railway | CO | | 1987 | 1987 | CSX Transportation | - |
| Columbia and Port Deposit Railroad | | PRR | 1858 | 1890 | Port Deposit Railroad | - |
| Columbia and Port Deposit Railway | | PRR | 1890 | 1916 | Philadelphia, Baltimore and Washington Railroad | - |
| Confluence and Oakland Railroad | | B&O | 1890 | 1941 | N/A | - |
| Consolidated Rail Corporation | CR | | 1976 | 1999 | CSX Transportation, Norfolk Southern Railway | - |
| Cumberland and Pennsylvania Railroad | C&PA, CPA | WM | 1850 | 1953 | Western Maryland Railway | - |
| Cumberland Valley Railroad | | PRR | 1860 | 1919 | Pennsylvania Railroad | - |
| Curtis Bay Railroad | CURB | B&O | 1915 | 1983 | Baltimore and Ohio Railroad | - |
| Delaware Railroad | | PRR | 1867 | 1976 | Consolidated Rail Corporation | - |
| Delaware and Chesapeake Railway | | PRR | 1878 | 1899 | Delaware Railroad | - |
| Delaware Coast Line Railroad | DCLR | | 1982 | 1994 | Maryland and Delaware Railroad | - |
| Delaware and Maryland Railroad | | PRR | 1832 | 1836 | Wilmington and Susquehanna Railroad | - |
| Delaware, Maryland and Virginia Railroad | | PRR | 1883 | 1956 | Philadelphia, Baltimore and Washington Railroad | - |
| Dorchester and Delaware Railroad | | PRR | 1866 | 1883 | Cambridge and Seaford Railroad | - |
| East Washington Railway | | | 1935 | 1976 | N/A | - |
| Eastern Shore Railroad | ESHR | | 1981 | 2006 | Bay Coast Railroad | - |
| Eastern Shore Railroad (1836–1884) | | PRR | 1836 | 1884 | New York, Philadelphia and Norfolk Railroad | - |
| Elkton and Middletown Railroad | | PRR | 1880 | 1916 | Philadelphia, Baltimore and Washington Railroad | - |
| Emmitsburg Railroad | | | 1868 | 1940 | N/A | - |
| Franklin Railroad | PRR | | 1859 | 1865 | Cumberland Valley Railroad | - |
| Franklin Railroad | | PRR | 1837 | 1850 | Chambersburg, Greencastle and Hagerstown Railroad | - |
| Frederick and Northern Railroad Company | | PRR | 1896 | 1897 | Hanover and York Railroad Company | - |
| Frederick and Pennsylvania Line Railroad Company (F&PL) | | PRR | 1867 | 1896 | Frederick and Northern Railroad Company | - |
| George's Creek and Cumberland Railroad | | WM | 1876 | 1917 | Western Maryland Railway | - |
| Green Ridge Railroad | | | 1883 | 1891 | N/A | Operated as a private carrier 1891-94 |
| Hagerstown and State Line Railroad | | WM | 1884 | 1899 | Washington and Franklin Railway | - |
| Kent County Railroad | | PRR | 1856 | 1877 | Baltimore and Delaware Bay Railroad | - |
| Lancaster, Cecil and Southern Railroad | | B&O | 1892 | 1972 | N/A | - |
| Maryland Central Railroad | | | 1867 | 1888 | Maryland Central Railway | - |
| Maryland Central Railway | | | 1888 | 1891 | Baltimore and Lehigh Railroad | - |
| Maryland and Delaware Railroad | | PRR | 1854 | 1877 | Delaware and Chesapeake Railway | - |
| Maryland and Delaware Coast Railway | | PRR | 1924 | 1932 | Maryland and Delaware Seacoast Railroad | - |
| Maryland and Delaware Seacoast Railroad | | PRR | 1932 | 1935 | Baltimore and Eastern Railroad | - |
| Maryland, Delaware and Virginia Railroad | | PRR | 1905 | 1905 | Maryland, Delaware and Virginia Railway | - |
| Maryland, Delaware and Virginia Railway | MDV | PRR | 1905 | 1923 | Baltimore and Eastern Railroad, Maryland and Delaware Coast Railway | - |
| Maryland and Pennsylvania Railroad | M&PA, MPA | | 1901 | 1985 | N/A | - |
| Maryland and Pennsylvania Terminal Railway | | | 1905 | 1985 | N/A | - |
| Metropolitan Railroad (Maryland) | | | 1853 | 1863 | N/A | Following the 1863 bankruptcy, B&O built its Metropolitan Branch along a similar route |
| Metropolitan Southern Railroad | | B&O | 1890 | 1988 | N/A | - |
| New Castle and Frenchtown Turnpike and Railroad Company | | PRR | 1828 | 1859 | N/A | - |
| New York, Philadelphia and Norfolk Railroad | | PRR | 1882 | 1958 | Penndel Company | - |
| Norfolk and Western Railroad | | N&W | 1881 | 1896 | Norfolk and Western Railway | - |
| Norfolk and Western Railway | N&W, NW | N&W | 1896 | 1998 | Norfolk Southern Railway | - |
| Northern Central Railway | | PRR | 1854 | 1976 | Consolidated Rail Corporation | - |
| Peninsula Railroad | | PRR | 1880 | 1882 | New York, Philadelphia and Norfolk Railroad | - |
| Penn Central Transportation Company | PC | | 1968 | 1976 | Consolidated Rail Corporation | - |
| Penndel Company | | PRR | 1954 | 1976 | Consolidated Rail Corporation | - |
| Pennsylvania Railroad | PRR | PRR | 1876 | 1968 | Penn Central Transportation Company | - |
| Pennsylvania Railroad in Maryland | | | 1876 | 1888 | George's Creek and Cumberland Railroad | - |
| Philadelphia and Baltimore Central Railroad | | PRR | 1854 | 1916 | Philadelphia, Baltimore and Washington Railroad | - |
| Philadelphia, Baltimore and Washington Railroad | | PRR | 1902 | 1976 | Consolidated Rail Corporation | - |
| Philadelphia, Wilmington and Baltimore Railroad | | PRR | 1838 | 1902 | Philadelphia, Baltimore and Washington Railroad | - |
| Piedmont and Cumberland Railway | | WM | 1886 | 1905 | Western Maryland Railroad | - |
| Pittsburgh and Connellsville Railroad | | B&O | 1837 | 1912 | Baltimore and Ohio Railroad in Pennsylvania | - |
| Port Deposit Railroad | | PRR | 1890 | 1890 | Columbia and Port Deposit Railway | - |
| Potomac Valley Railroad | | WM | 1890 | 1905 | Western Maryland Railroad | - |
| Preston Railroad | | | 1897 | 1960 | N/A | - |
| Queen Anne's Railroad | | PRR | 1894 | 1905 | Maryland, Delaware and Virginia Railroad | - |
| Queen Anne's and Kent Railroad | | PRR | 1856 | 1899 | Delaware Railroad | - |
| Shenandoah Valley Railroad | | N&W | 1870 | 1890 | Shenandoah Valley Railway | - |
| Shenandoah Valley Railway | | N&W | 1890 | 1890 | Norfolk and Western Railroad | - |
| Smyrna and Delaware Bay Railroad | | PRR | 1865 | 1902 | N/A | - |
| Southern Maryland Railroad | | | 1868 | 1886 | Washington and Potomac Railroad | - |
| State Line and Oakland Railroad | | B&O | 1889 | 1890 | State Line and Oakland Railway | - |
| State Line and Oakland Railway | | B&O | 1890 | 1890 | Confluence and Oakland Railroad | - |
| Union Railroad of Baltimore | | PRR | 1866 | 1976 | Consolidated Rail Corporation | - |
| Virginia and Maryland Railroad | VAMD | | 1977 | 1981 | Eastern Shore Railroad | - |
| Washington, Brandywine and Point Lookout Railroad | | | 1918 | 1942 | U.S. Navy | - |
| Washington & Chesapeake Beach Railway | | | 1891 | 1895 | Chesapeake Beach Railway | - |
| Washington City and Point Lookout Railroad | | B&O | 1872 | 1874 | Baltimore and Ohio Railroad | - |
| Washington County Railroad | | B&O | 1864 | | | - |
| Washington and Franklin Railway | | WM | 1899 | | | Owned by Reading Company and leased to Western Maryland Railway; still exists as a lessor of CSX Transportation, owned by Reading International, Inc. |
| Washington and Potomac Railroad | | | 1886 | 1900 | Washington, Potomac and Chesapeake Railroad | - |
| Washington, Potomac and Chesapeake Railroad | | | 1901 | 1910 | Washington, Potomac and Chesapeake Railway | - |
| Washington, Potomac and Chesapeake Railway | | | 1910 | 1918 | Washington, Brandywine and Point Lookout Railroad | - |
| West Virginia Central and Pittsburg Railway | | WM | 1882 | 1905 | Western Maryland Railroad | - |
| Western Maryland Railroad | | WM | 1853 | 1909 | Western Maryland Railway | - |
| Western Maryland Railway | WM | WM | 1909 | 1989 | CSX Transportation | - |
| Western Maryland Tidewater Railroad | | WM | 1883 | 1905 | Western Maryland Railroad | - |
| Wicomico and Pocomoke Railroad | | PRR | 1848 | 1890 | Baltimore and Eastern Shore Railroad | - |
| Wilmington and Susquehanna Railroad | | PRR | 1836 | 1838 | Philadelphia, Wilmington and Baltimore Railroad | - |
| Worcester Railroad | | PRR | 1853 | 1883 | Delaware, Maryland and Virginia Railroad | - |
| Worcester and Somerset Railroad | | PRR | 1867 | 1880 | Peninsula Railroad | - |
| Hanover and York Railroad Company | | PRR | 1897 | 1914 | York, Hanover and Frederick Railway Company | - |
| York, Hanover and Frederick Railway Company | | PRR | 1914 | 1954 | Penndel Company | - |