Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| Name | Mark | System | From | To | Successor | Notes |
| --- | --- | --- | --- | --- | --- | --- |
| Alexandria and Fredericksburg Railway |  | RF&P | 1872 | 1890 | Baltimore and Potomac Railroad |  |
| Alexandria and Washington Railroad |  | RF&P | 1854 | 1872 | Alexandria and Fredericksburg Railway |  |
| Baltimore and Ohio Railroad | B&O, BO | B&O | 1831 | 1987 | Chesapeake and Ohio Railway |  |
| Baltimore and Potomac Railroad |  | PRR | 1867 | 1902 | Philadelphia, Baltimore and Washington Railroad |  |
| Chesapeake Beach Railway |  |  | 1896 | 1935 | East Washington Railway |  |
| Chesapeake and Ohio Railway | C&O, CO | C&O | 1891 | 1987 | CSX Transportation |  |
| Consolidated Rail Corporation | CR |  | 1976 | 1999 | CSX Transportation/Norfolk Southern Railway |  |
| East Washington Railway |  |  | 1935 | 1976 | N/A |  |
| Georgetown Barge, Dock, Elevator and Railway Company |  | B&O | 1888 | 1972 | Baltimore and Ohio Railroad |  |
| Orange, Alexandria and Manassas Railroad |  | SOU | 1872 | 1872 | Virginia and North Carolina Railroad |  |
| Penn Central Transportation Company | PC |  | 1968 | 1976 | Consolidated Rail Corporation |  |
| Pennsylvania Railroad | PRR | PRR | 1918 | 1968 | Penn Central Transportation Company |  |
| Philadelphia, Baltimore and Washington Railroad |  | PRR | 1902 | 1976 | Consolidated Rail Corporation |  |
| Philadelphia, Wilmington and Baltimore Railroad |  | PRR | 1891 | 1902 | Philadelphia, Baltimore and Washington Railroad |  |
| Richmond and Danville Railroad |  | SOU | 1886 | 1894 | Southern Railway |  |
| Richmond, Fredericksburg and Potomac Railroad | RF&P, RFP | RF&P | 1920 | 1991 | Richmond, Fredericksburg and Potomac Railway |  |
| Richmond, Fredericksburg and Potomac Railway | RFP |  | 1991 |  |  | Still exists as a subsidiary of CSX Transportation |
| Southern Railway | SOU | SOU | 1894 | 1990 | Norfolk Southern Railway |  |
| Southern Maryland Railroad |  |  | 1882 | 1886 | Washington and Potomac Railroad |  |
| Virginia Midland Railway |  | SOU | 1880 | 1886 | Richmond and Danville Railroad |  |
| Virginia and North Carolina Railroad |  | SOU | 1872 | 1873 | Washington City, Virginia Midland and Great Southern Railway |  |
| Washington, Alexandria and Georgetown Railroad |  | RF&P | 1862 | 1868 | Alexandria and Washington Railroad |  |
| Washington City and Point Lookout Railroad |  | B&O | 1873 | 1874 | Baltimore and Ohio Railroad |  |
| Washington City, Virginia Midland and Great Southern Railway |  | SOU | 1873 | 1880 | Virginia Midland Railway |  |
| 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 | Chesapeake Beach Railway |  |
| Washington Southern Railway | WSN | RF&P | 1901 | 1920 | Richmond, Fredericksburg and Potomac Railroad |  |
| Washington Terminal Company | WATC | B&O/ PRR | 1901 |  |  | Still exists as a subsidiary of the National Railroad Passenger Corporation (Amtrak) |
| Washington and Western Maryland Railroad |  | B&O | 1889 | 1985 | N/A |  |
Question:
what is the only now defunct railroad that existed for 156 years?
Answer:
Baltimore and Ohio Railroad