This line is the Pope's Creek subdivision of CSX-formerly Conrail, PennCentral, Pennsylvania and the Philadelphia, Wilimington and Baltimore.
The line started out as the Baltimore and Potomac after the War Between The States. (Actually it was chartered before the war, but construction did not begin until after 1865.)
Southern Maryland farmers were looking for a more reliable way to ship produce to market than having to rely on river steamers plying the Potomac and Chesapeake Bay.
The line originated in Baltimore, headed southwest towards Washington and then went south at Bowie* to Popes Creek, on the Potomac, in Charles County, about 10 miles southwest of La Plata. The first train on the line made its trip on New Year's Day, 1873.
(*Supposedly, the Baltimore and Ohio Railroad was so powerful in the Maryland state legislature that it was written into the state charter that no other railroad could build a competing line between Baltimore and Washington. The B&P's line to Bowie included a "branch" to Washington, DC. This eventually became the Pennsylvania Railroad's famed four-track mainline. Bowie was originally known as the City of Huntington (not to be confused with Huntingtown in Calvert County) but was renamed in honor of Governor Oden Bowie who helped secure financing for the railroad, backed by PRR interests.)
Currently this line serves TWO power plants-Morgantown, on the Potomac, in Charles County and Chalk Point, on the Patuxent, in Prince George's County. The line branches off in Brandywine, near the route 381 crossing and the Brandywine firehouse. (The line to Popes Creek was torn up in the late 1960's. For a number of years the line ran no further than La Plata until the Morgantown power plant was completed.)
There are sidings in Collington and La Plata in addition to the siding in Brandywine. There is also Long Siding on the Herbert Sub which can be seen next to the Brandywine firehouse.
In addition to the coal traffic (loads south, empties north), there is a twice weekly local that serves a couple of lumber companies and an ink company in Waldorf and White Plains.
Additionally, there was a new siding put in place last (2005) summer to serve a gravel operation north of La Plata on Rosewick Road. This operation has its own switcher, either a GP-7 or GP-9 that can be viewed from Rosewick Road. Gravel trains usually operate on Monday-Wednesday-Friday at night.
As far as I know the line is unsignalled except for the approach to the NEC (NorthEast Corridor) in Bowie. Dispatching is done by radio, radio traffic can be monitored on 161.07 MHz.
Croome and Croom are the same place. Somewhere in the early 1900's the old English spelling fell out of favor.
This line does NOT go to Quantico-the line through Quantico is the old Richmond, Fredricksburg and Potomac Railroad mainline between Richmond and Washington and is on the Virginia side of the Potomac.
The line to Chesapeake Beach was the appropriately named "Chesapeake Beach Railway", built by Otto Mears, of Colorado railroad fame. Back before the Chesapeake Bay bridge was even thought of, Chesapeake Beach was a resort area frequented by residents of Washington and environs. The CBRy crossed the Pope's Creek line somewhere in Upper Marlboro-the bridge abutments are still in place.
The line to Chalk Point is known as the "Herbert Sub". After branching off in Brandywine, it follows the roadbed of the Washington, Brandywine and Point Lookout* for a portion of its journey to Chalk Point.
*Also had other names during its coporate lifetime including the Washington, Chesapeake and Potomac.
(The grandiosely named WB&Pt.L only ever ran between Brandywine and Mechanicsville in St. Mary's County. It was extended to the Patuxent River Naval Air Station during World War II with the operation being taken over by the U. S. Navy. This line was abandoned in the late 1960's and torn up in the early 1970's.)
There are railroad museums in both La Plata and Bowie where you should be able to find more information on the line. (The La Plata Train Station Museum is open from 11AM-4PM on Saturdays and Sundays during the summer months.)
Additionally, Charles County historian John Wearmouth wrote a booklet on the B&P sometime in the 1980's. I do not know if copies are still available.
For more information on the Pope's Creek sub:
A concise history of the line:
Map of the lines in question:
Timetable for the Pope's Creek Secondary:
Timetable for the Herbert Secondary:
For more information on the Chesapeake Beach Railway:
The City of Bowie railroad museum:
(Scroll down midway through the page.)
Photo of the first passenger train through Brandywine after the Baltimore and Potomac became a part of the Philadelphia, Wilmington and Baltimore in 1895: