While mapping Mark Twain's railroad journeys I became curious about the railroad he mentioned attempting to find humor in his disdain for American Indians. "There is an impression abroad that the Baltimore and Washington Railroad Company and many of its employees are Goshoots; but it is an error."
I have found no reference for this particular line, by this name. In 1870, the only line servicing Washington DC to the states was the Baltimore and Ohio (B&O). A second line did not come into play until 1872, the Baltimore and Potomac, controlled by the Pennsylvania Railroad.
It is apparent that the name “Baltimore and Washington” was in common usage yet it does not appear in any documentation on the history of the railroads in this region. Perhaps the most telling reference is an etching of the Thomas viaduct, built by the Baltimore and Ohio railroad sometime between July 4, 1833 and July 4, 1835.
The United States Illustrated, Charles A. Dana, Editor. Published for: Hermann J. Meyer, New York, Public domain, via Wikimedia Commons
The route that includes this viaduct is not found in the collection of kmz files available from the University of Nebraska site but it is found on the USGS topographic map (KML overlay) for Baltimore, MD (1894) and Relay, MD (1894). The UN kmz files show the old route for the B&O along the north side of the Patapsco River. They do not indicate a crossing of the river at the site of the viaduct.
The so-called Baltimore and Washington RR track exists today as the Capitol Subdivision. It was originally referred to as the Washington Branch of the B&O.
What the kmz files do indicate is the Baltimore and Potomac Railroad branching from the B&O line at the point where the two lines actually cross, near the site of the viaduct. The UN kmz files are apparently in error . They do not, however, continue the route to the city of Baltimore , where the Baltimore and Potomac actually originated (and would be premature in inclusion in this collection of files). This particular line did not operate before 1872.