I was interested in the position of Comet Pong Pong as demonstrated in this image (posted by @contrarianism): https://sli.mg/HhRn1Z

Namely, what would be the significance of that location through history. I wasn't getting very far searching the address so thought I'd have a look at a map.

I found this map from 1913, which shows the general area: http://cdn.ghostsofdc.org/wp-content/uploads/2016/09/26224041/ca000117.jpg

I then Photoshopped that map onto a screenshot from Google Maps, and noticed that there appears to be an underground stream that runs right underneath Buck's Fishing and Camping, past an old graveyard site: https://imgur.com/a/HnMhF

The stream is called Broad Branch, and parts of it have been restored, but not as far along as where Comet and Buck's are located, I guess because it's too built up. This would mean though that there should still be a tunnel underneath there, albeit a wet one, and according to my map, there could be an access point to it in the car park at the back of the buildings. http://news.nationalgeographic.com/news/2014/11/141125-dc-daylighting-broad-branch-stream-restoration-science/

Probably nothing, but I found it a fun exercise all the same! :)

As for there being an historical monument of note at the location of Comet, there doesn't appear to be anything there 100 years ago- boo.