Table:
Name | Mark | System | From | To | Successor | Notes
Alexandria and Fredericksburg Railway |  | RF&P | 1872 | 1890.0 | Baltimore and Potomac Railroad | 
Alexandria and Washington Railroad |  | RF&P | 1854 | 1872.0 | Alexandria and Fredericksburg Railway | 
Baltimore and Ohio Railroad | B&O, BO | B&O | 1831 | 1987.0 | Chesapeake and Ohio Railway | 
Baltimore and Potomac Railroad |  | PRR | 1867 | 1902.0 | Philadelphia, Baltimore and Washington Railroad | 
Chesapeake Beach Railway |  |  | 1896 | 1935.0 | East Washington Railway | 
Chesapeake and Ohio Railway | C&O, CO | C&O | 1891 | 1987.0 | CSX Transportation | 
Consolidated Rail Corporation | CR |  | 1976 | 1999.0 | CSX Transportation/Norfolk Southern Railway | 
East Washington Railway |  |  | 1935 | 1976.0 | , 
Georgetown Barge, Dock, Elevator and Railway Company |  | B&O | 1888 | 1972.0 | Baltimore and Ohio Railroad | 
Orange, Alexandria and Manassas Railroad |  | SOU | 1872 | 1872.0 | Virginia and North Carolina Railroad | 
Penn Central Transportation Company | PC |  | 1968 | 1976.0 | Consolidated Rail Corporation | 
Pennsylvania Railroad | PRR | PRR | 1918 | 1968.0 | Penn Central Transportation Company | 
Philadelphia, Baltimore and Washington Railroad |  | PRR | 1902 | 1976.0 | Consolidated Rail Corporation | 
Philadelphia, Wilmington and Baltimore Railroad |  | PRR | 1891 | 1902.0 | Philadelphia, Baltimore and Washington Railroad | 
Richmond and Danville Railroad |  | SOU | 1886 | 1894.0 | Southern Railway | 
Richmond, Fredericksburg and Potomac Railroad | RF&P, RFP | RF&P | 1920 | 1991.0 | 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 | 1990.0 | Norfolk Southern Railway | 
Southern Maryland Railroad |  |  | 1882 | 1886.0 | Washington and Potomac Railroad | 
Virginia Midland Railway |  | SOU | 1880 | 1886.0 | Richmond and Danville Railroad | 
Virginia and North Carolina Railroad |  | SOU | 1872 | 1873.0 | Washington City, Virginia Midland and Great Southern Railway | 
Washington, Alexandria and Georgetown Railroad |  | RF&P | 1862 | 1868.0 | Alexandria and Washington Railroad | 
Washington City and Point Lookout Railroad |  | B&O | 1873 | 1874.0 | Baltimore and Ohio Railroad | 
Washington City, Virginia Midland and Great Southern Railway |  | SOU | 1873 | 1880.0 | Virginia Midland Railway | 
Washington and Potomac Railroad |  |  | 1886 | 1900.0 | Washington, Potomac and Chesapeake Railroad | 
Washington, Potomac and Chesapeake Railroad |  |  | 1901 | 1910.0 | Washington, Potomac and Chesapeake Railway | 
Washington, Potomac and Chesapeake Railway |  |  | 1910 | 1918.0 | Chesapeake Beach Railway | 
Washington Southern Railway | WSN | RF&P | 1901 | 1920.0 | 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 | 1985.0 |  |

Question: what now defunct railroad existed for the shortest time?
Answer: Orange, Alexandria and Manassas Railroad

Question: how many railroads became defunct in the 1880's, and how many became defunct in the 1980's?
Answer: 3|3

Question: name one other railroad that was under the rf&p system other than alexandria and washington railroad.
Answer: Alexandria and Fredericksburg Railway

Question: was the pennsylvania railroad under the prr or the rf&p?
Answer: PRR

Question: what is the only now defunct railroad that existed for 156 years?
Answer: Baltimore and Ohio Railroad