A while ago in this blog, I wrote a post called Walking the Gold Mine Loop, about the trail system in the woods near the Great Falls of the Potomac on the Maryland side of the river. The loop trail is named for the gold mine that once operated here. That post has received a small but steady stream of hits, so I thought I’d do an update, about what I’ve recently learned about this area.
“Historic Mining Along the C&O Canal”
As a volunteer at the Chesapeake and Ohio Canal National Historical Park, I recently attended a presentation by Jessica Lindsay, who had completed a Geoscientists-in-the-Parks internship here. She had been tasked with mapping mining structures throughout the entire park and identifying current hazards related to these sites.
There was quite a lot of mining over the years along the 185-mile canal, for concrete, lime, sandstone, coal, iron, and gold. While little in the way of technological ruins remain, the landscape still bears lasting signs of mining. For example, Lindsay showed us images from west of Harpers Ferry, West Virginia, showing long gashes in the landscape up to 70 feet deep from iron mining. Most evidence of mining within the park is much more subtle.
Her talk, “Historic Mining Along the C&O Canal,” focused mainly on the Great Falls area and its many defunct gold mines, in particular the Maryland Mine, which the Gold Mine Loop and its connecting trails overlie. Mining took place near Great Falls from the 1880s to the 1940s, when the Maryland Mine closed.
The gold veins threading through the hills here are the northernmost end of a gold-bearing belt that extends all the way to Georgia. Gold nuggets weren’t panned from streambed sediments here, as in California during the gold rush years of the mid-1800s. Instead, the gold-bearing rock here had be crushed into small pieces and then the gold extracted using mercury. It was a laborious, dangerous, and poisonous process. Because of the relatively minor amounts extracted, it ultimately proved unprofitable.
Lindsay clarified some mining terms for us. A tunnel is a chamber that has openings on both ends, like a train tunnel. An adit has only one opening; it leads to a dead end. A shaft is a vertical chamber. Don’t step into one.
Gold Mines at Great Falls
One of the sources Lindsay relied on was the Department of the Interior’s Geological Survey Bulletin 1286, “Gold Veins Near Great Falls, Maryland,” published in 1969. Most of the text is heavy duty geology, but the 22-page bulletin also contains interesting historical background and some intriguing photos and graphics.
Consider the cover illustration, created from a historical photograph reproduced in the bulletin. It shows the processing facility for the Maryland Mine. The caption for the photo explains what role the various parts of this structure played in the gold extraction process. Knowledgeable locals know that the remains of this facility—a concrete structure that supported a water tower—can be seen in the woods on the left as you enter the C&O Canal National Historical Park from MacArthur Boulevard. Last year, the National Park Service removed some wooden structures from here that were not historic or even historically accurate. They were built in the 1980s to help interpret the site for visitors but had deteriorated and become hazardous.
As you walk the trails through the woods here, you’ll see little other obvious evidence that mining took place here. And yet, there is much among the trees that just doesn’t look quite right. “If it doesn’t look natural,” Lindsay said, “it most likely isn’t.” There are earthworks and stone structures dating back to the Civil War, traces of old roads, and exploratory prospecting pits and trenches from the mining operation.
One illustration in the bulletin reveals how extensive the Maryland Mine was. A cutaway view shows the mine’s underground chambers in 1940, when the mine closed, and the above-ground structures as they appeared in 1967. Long horizontal passageways pierce the bedrock at depths of 50 feet, 100 feet, 135 feet, and 200 feet. That is what’s below you when you walk the Gold Mine Loop.
Openings to the mines throughout the park have been sealed for obvious safety reasons. In some places bat gates, grates that allow bats to fly in and out, have been installed. But minor openings remain, some resulting from structural failures. However enticing, these places are dangerous. They can, have, and do collapse. In the unlikely event that you ever happen upon one, don’t try to enter it!
The Topographical View
One of the tools Lindsay used to locate evidence of mining was the MD iMap Topography Viewer, a nifty web application you can access yourself. It is basically a high-resolution map of Maryland that shows topographical features in great detail. The data was last updated in February 2019, so it’s pretty current. I zoomed in on the area where the Maryland Gold Mine was located and made a copy of the image on my screen. I added the three red letters to the image below to help point out some features.
The Potomac River is the flat area running from top to bottom on the left. “A” shows the location of Great Falls Tavern, the visitor center for this section of the C&O Canal National Historical Park. (Buildings are only faintly visible.) The long linear feature running past the tavern is the canal itself. You can discern individual locks and other structures, including the stop gate across the canal and the adjacent levee, both built for flood control, in the lower part of the image.
“B” marks a distinct feature unrelated to mining: the turnaround for a trolley that connected Great Falls to nearby Bethesda in the early 20th century. The trolley tracks are gone, but a trail now follows the trolley route through the woods.
The “M” toward the lower right of the image marks the site of the Maryland Mine gold processing facility (depicted on the Geological Survey Bulletin 1286 cover), near the intersection of MacArthur Boulevard and Falls Road, which are faintly visible. The areas to the right and upper right are now neighborhoods, some built atop old gold mines.
Look below the “M” and in other areas throughout the hilly, undeveloped land between MacArthur Boulevard and the canal, and you can pick out countless disturbances in the landscape—gashes, lines, pits, mounds—topographical evidence of the mining operations that once took place here and that are only vaguely apparent from the trails in the woods.
Call up the topography viewer and play around with it yourself. It’s fascinating! Take a look at your own neighborhood. You may see features you never realized existed.
The Gold Mine Loop is one of my favorite places to walk. Since Jessica Lindsay’s talk, I’m eager to get back into the woods. I’ll look around now with greater interest, curious about just what it is I am seeing and what lies beneath.
David Romanowski, 2020