| Name | Mark | System[nb 1] | From | To | Successor | Notes |
| Baltimore and Delaware Bay Railroad | | PRR | 1881 | 1902 | Delaware Railroad |
| Baltimore and Ohio Railroad | B&O, BO | B&O | 1886 | 1987 | Chesapeake and Ohio Railway |
| Baltimore and Philadelphia Railroad | | B&O | 1883 | 1989 | CSX Transportation |
| Brandywine Valley Railroad | BVRY | | 1999 | 2005 | East Penn Railways |
| Breakwater and Frankford Railroad | | PRR | 1873 | 1883 | Delaware, Maryland and Virginia Railroad |
| Cambridge and Seaford Railroad | | PRR | 1882 | 1899 | Delaware Railroad |
| Chesapeake and Ohio Railway | CO | | 1987 | 1987 | CSX Transportation |
| Consolidated Rail Corporation | CR | | 1976 | 1999 | CSX Transportation, Norfolk Southern Railway |
| Delaware Railroad | | PRR | 1836 | 1976 | Consolidated Rail Corporation |
| Delaware and Chesapeake Railway | | PRR | 1877 | 1899 | Delaware Railroad |
| Delaware and Chester County Railroad | | B&O | 1867 | 1869 | Wilmington and Western Railroad |
| Delaware, Maryland and Virginia Railroad | | PRR | 1883 | 1956 | Philadelphia, Baltimore and Washington Railroad |
| Delaware and Pennsylvania Railroad | | PRR | 1857 | 1873 | Pennsylvania and Delaware Railway |
| Delaware and Pennsylvania State Line Railroad | | RDG | 1865 | 1866 | Wilmington and Reading Railroad |
| Delaware Coast Line Railroad | DCLR | | 1982 | 2018 | Delmarva Central Railroad |
| Delaware Valley Railway | DV | | 1994 | 1999 | Brandywine Valley Railroad |
| Delaware Western Railroad | | B&O | 1877 | 1883 | Baltimore and Philadelphia Railroad |
| Dorchester and Delaware Railroad | | PRR | 1867 | 1883 | Cambridge and Seaford Railroad |
| East Penn Railways | EPRY | | 2005 | 2007 | East Penn Railroad |
| Junction and Breakwater Railroad | | PRR | 1857 | 1883 | Delaware, Maryland and Virginia Railroad |
| Kent County and Delaware Bay Railroad[1] | | | | | |
| Lewes and Millsboro Railroad | | PRR | 1835 | 1873 | Breakwater and Frankford Railroad |
| Maryland and Delaware Railroad | | PRR | 1857 | 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 | Delaware, Maryland and Virginia Railroad |
| Maryland, Delaware and Virginia Railroad | | PRR | 1905 | 1905 | Maryland, Delaware and Virginia Railway |
| Maryland, Delaware and Virginia Railway | | PRR | 1905 | 1923 | Maryland and Delaware Coast Railway |
| New Castle and Frenchtown Turnpike and Railroad Company | | PRR | 1828 | 1877 | Philadelphia, Wilmington and Baltimore Railroad |
| New Castle Turnpike and Railroad Company | | PRR | 1829 | 1830 | New Castle and Frenchtown Turnpike and Railroad Company |
| New Castle and Wilmington Railroad | | PRR | 1839 | 1877 | Philadelphia, Wilmington and Baltimore Railroad |
| Newark and Delaware City Railroad | | PRR | 1880 | 1881 | Pomeroy and Newark Railroad |
| Octoraro Railway | OCTR | | 1977 | 1994 | Delaware Valley Railway |
| Penn Central Transportation Company | PC | | 1968 | 1976 | Consolidated Rail Corporation |
| Pennsylvania Railroad | PRR | PRR | 1918 | 1968 | Penn Central Transportation Company |
| Pennsylvania and Delaware Railway | | PRR | 1873 | 1879 | Newark and Delaware City Railroad |
| Philadelphia, Baltimore and Washington Railroad | | PRR | 1902 | 1976 | Consolidated Rail Corporation |
| Philadelphia and Reading Railway | P&R | RDG | 1900 | 1924 | Reading Company |
| Philadelphia, Wilmington and Baltimore Railroad | | PRR | 1838 | 1902 | Philadelphia, Baltimore and Washington Railroad |
| Pomeroy and Newark Railroad | | PRR | 1881 | 1917 | Philadelphia, Baltimore and Washington Railroad |
| Queen Anne's Railroad | | PRR | 1895 | 1905 | Maryland, Delaware and Virginia Railroad |
| Reading Company | RDG | RDG | 1924 | 1976 | Consolidated Rail Corporation |
| Smyrna and Delaware Bay Railroad | | PRR | 1865 | 1902 | N/A |
| Wilmington and Brandywine Railroad | | RDG | 1861 | 1865 | Delaware and Pennsylvania State Line Railroad |
| Wilmington and Northern Railroad | | RDG | 1877 | 1976 | Consolidated Rail Corporation |
| Wilmington and Reading Railroad | | RDG | 1866 | 1876 | Wilmington and Northern Railroad |
| Wilmington and Susquehanna Railroad | | PRR | 1832 | 1838 | Philadelphia, Wilmington and Baltimore Railroad |
| Wilmington and Western Railroad | | B&O | 1869 | 1877 | Delaware Western Railroad |
