Thank you for the responses! What sparked my interest was a notice I found in an old book last week:
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Since my post, I've found this photo of the Pomeroy Tunnel on DPL:
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Seems awfully high up on the mountain for a railroad tunnel. I also found this humorous postcard pic:
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The tunnel comes out at this location in red on the USGS map, which correlates well with Jeff Young's location:
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Also discovered this old newspaper story from an interview with Pomeroy himself:
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Here's the west end on Google Earth based on the map in Jeff Ramsey's link:
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Again, a fair piece up the hill for a supposed railroad tunnel.
Thank you all,
Matt