That's what I originally thought. The negative envolope said it is the "Wye at Summit Colo." The date is listed as 1907 and the road is Denver Boulder & Western. I was somewhat suspicious because the C&N didn't become the DB&W until 1909.
I only know of three wyes on the C&N: Sunset, Newmarket, and Sulphide. There are decent photos of Sunset and Newmarket, and this definately isn't one of those. It looks a lot like Sulphide (just before Eldora), so that where I originally though this was.
I went to Sulphide area recently, and I couldn't get the mountains in the background to match, particularly those two peaks in the background.
Here's the old photo again, then one I took on Thanksgiving day from near where the Lake Eldora road branches off the road to Eldora:
The C&N/DB&W grade should be just above the rooftops for the two buildings in the background. From the milepost location, Sulphide station should be to the left of my photo. There aren't any hills in that direction that are even close to this photo. I don't know quite where the Sulphide wye was located.