Using USGS Historic Maps To (Partially) Unravel A Trail Mystery

This past weekend Shira and I were tramping through Turkey Run along the Potomac Heritage trail when I noticed what appeared to be a toppled chimney on the ridge above:

I couldn't resist going off trail to explore the area. What gem might be hiding there? To my surprise, I found quite a bit of debris:

Clearly some structure used to occupy the ridge, and when it did, it had quite the view. Here's a few more snapshots of the area:

As I poked around the site, not one, but two turkeys took flight, no doubt fleeing for their life. I had no idea turkeys could fly and I kick myself for not snapping a few photos. But yeah, that definitely happened.

While I was psyched that I found a new feature in the area to photograph, I was bummed to have no idea what the heck I was looking at. Was the structure old or important? Or, was it just a park service outbuilding from a couple of years ago?

I still don't know the answer, but I do believe I've found a few important clues. While doing research on USGS maps I found the USGS Historical Map Explorer. This sweet little maps application allows you to select an area in US and see historic maps that are available. You can interactively browse these maps. For example, here's what Arlington, VA looked like in the 1890's. You can overlay multiple year's maps and adjust their opacity to compare them simultaneously. You can also download the maps as PDF files and load them into Avenza Maps to have them on your mobile phone.

While this is all very cool, I didn't have a practical use for this tool. Until now.

Using the historic maps tool I loaded up the Falls Church quadrangle from 1945, 1951 and 1956. Here's screenshots of each map:

If you click on the maps you'll notice that in 1945 and 1951 there was indeed a road and a building where I took my snapshots. (Whooo!) In 1956 the building is no longer shown on the map, but a gauging station is. Along the Potomac Heritage Trail, near where I snapped these photos is this structure:

From a Google Images search, appears to be a gauging station (look at that, a bonus mystery solved!).

So while I don't know the full story behind the ruins, it does appear that the debris I found dates back as far as 1945.

Using the USGS Historic Tools was the closest I've come to having one of those CSI magical tech moments; you know were a TV tech geek pulls up some esoteric information in a matter of seconds. Whoo!

Next time I'm planning a hike I'll have to consult the USGS historic maps. Hiking is fun, but playing Indiana Jones in search of a lost city *and* hiking is even better.