I stumbled on this really fascinating article about quarrying on the Potomac River, something that I had never heard of. I knew that Smoot Sand & Gravel, a major customer for the B&O’s Georgetown Branch, did dredging in the Potomac River for sand and gravel, but I did not know they did quarrying, and to such a large scale! Apparently there were many, many quarries located on the Potomac shores which were all abandoned some time in the late 1930s/early 1940s. This article outlines some of those details and shows the location of one such quarry with equipment still left behind. Amazing. I will have to go!
https://blogs.weta.org/boundarystones/2017/06/13/little-italy-under-parkway
Ben: Great piece of history. You may enjoy a similar piece describing a site just east of Wheaton, MD: http://www.fosc.org/MysteryRuins.htm
I’m sure you are aware of the cement plant once found at the eastern terminus of the GB; it hosted a fairly extensive (for DC) collection of team tracks. Any photos or history on that enterprise?