While studying maps of western McLean, Va, where I grew up, I uncovered a mystery.
In 1902, magnate John McLean and politician Stephen Elkins started building a trolley line from Washington, DC, to Great Falls Park (photo at left; see Wikipedia). The tracks show up on maps from 1904 until their removal in the 1930s. The roadbed became Old Dominion Drive, one of the “main streets” of McLean, Va.
Here’s the mystery: The earliest maps showing the tracks between McLean and Great Falls route them differently from today’s Old Dominion Drive. The older maps show the tracks crossing Georgetown Pike near Madeira School, at a village called “Prospect Hill.” The tracks then cross Difficult Run next to the Pike’s bridge. Starting in about 1915, maps show the tracks following today’s Old Dominion Drive.
Why did it change? Was the first map wrong? That seems most likely to me, but still pretty surprising. I’m asking around for evidence that the tracks might have moved. I doubt there is any, but it’s worth investigating. [See update in a newer post]