I hate to dispute you, this being my first post here, but the history of the line dates to just after the War Between the States. The Southern Maryland Railroad was incorporated in 1868 with construction beginning a short time later. Construction was begun in Brandywine (connecting with the, at that time, Baltimore & Potomac Railroad) and was built in a southeasterly direction with the intention of going all the way to Point Lookout. The line went into its first of many bankruptcies in 1886 and emerged as the Washington & Potomac Railroad. The line only ever ran as far south as Mechanicsville (sometimes listed as "Forrest Hall")*. In 1901, the line went through another bankruptcy and emerged as the Washington, Potomac & Chesapeake Railway. At the end of 1917 the line again found itself in bankruptcy and was very nearly scrapped due to the high price of scrap metal during WW1. However, farmers in the area were able to purchase the line from a salvage firm and in June of 1918 the line began running again, this time under the name of the Washington, Brandywine & Point Lookout Railroad.
In the 1930's, revenues were dropping due to increased competition from the automobile and the line probably would have been gone for good except for the intervention of WW2.
*In June of 1942, the US Navy took over the line and extended it to the Patuxent River Naval Air Station. As late as the mid-1950's the Navy was still operating the line. In fact, the Navy operated an "accomodation" train that connected with the Pennsylvania Railroad in Brandywine until the PRR stopped passenger trains on the Pope's Creek Line in 1949. In the late 1950s/early 1960s, operation of trains on the line was turned over to the PRR. One of the primary products on the line was aviation fuel taken to the base. However, that started coming in by barge and the importance of the line dwindled. The PRR operated an occasional train to the base into the late 1960s. When train operation ceased, the line was offered for sale by the GSA but there were no takers and the line was scrapped in the mid-1970's.
The Pax River website used to have a photo of a U. S. Navy 0-6-0T steam switch engine-haven't been to the website recently, so I don't know if its still there.
The "converted truck" mentioned by Railroad was actually a gasoline powered locomotive built by the FWD (Four Wheel Drive) Corporation, based on a WW1 truck chassis.
Part of this line is still used for the trackage that runs from Brandywine to the Chalk Point Generating station.
A good website for the line that still runs to the Chalk Point and Morgantown (Charles County) generating stations can be found here:
Popes Creek Sub website
Check out the "History" section for more on the WB&Pt.L.
A couple of obscure references, if you can find them:
"Farmers' Railroad" by Frank Donovan, Jr., Railroad Magazine, March 1939
"Brake shoes aweigh!" by E. John Long, Trains Magazine, March 1953
Another article I have about self-propelled railcars shows that the WB&PtL had two such cars-the first the aforementioned FWD car, listed as having a Wisconsin 62HP gas engine, weighing in at 9 tons, with a length of 22' 2". The car/loco had 5 windows, with a capacity for 15 passengers and a baggage compartment.
The second was a Brill-White car with a 4 cylinder gas engine, with a length of 18' 9", having a capacity for 20 passengers.
I also have a copy of a builders photo of a steam locomotive lettered "Washington, Brandywine & Pt. Lookout, No. 5". The locomotive has a 2-6-0 wheel arrangement built by Baldwin Locomotive Works of Philadelphia in 1924 (construction# 58005). The locomotive had a 52" diameter boiler, 15"x20" cylinders and driving wheels 42" in diameter. The locomotive has an odd look, appearing to sit up high on such short diameter drivers.
It was sold in 1938 to the Housatonic Tunnel and Wilmington and scrapped in 1949.
For a history of the Chesapeake Beach Railway, and the stillborn Drum Point extension:
"Otto Mears Goes East-The Chesapeake Beach Railway" by Ames W. Williams
(Copies may still be available at the Chesapeake Beach Railway Museum, near the "Rod & Reel Restaurant")
Chesapeake Beach Railway Museum website
If you're inclinded to walk the Wye in Brandywine, where the line through La Plata connects with the Chalk Point line, you can still make out where the water tower stood. The concrete footers and stand (water) pipe are still in place. Best to do so in the early spring before the snakes, ticks and vegetation overtake the area.
There is a gentleman named Paul Rogers who used to work at Pax River (now retired) who has collected an extensive amout of information on the WB&Pt.L if anyone knows how to contact him.