There's a selection of videos you can watch on YouTube that will give you an idea about travelling up and over Wolf Creek Pass, including the CW McCall song about it...long before the improvements were made to both sides. September is a great time to be in that area of Colorado, was down there a few years back in late September and the colours were so vibrant.
It's really not a difficult crossing any more. Even with the potential for snow in September, CDOT does a great job in keeping it open if it does snow, and that early in the season will likely melt off quickly.
There's also N La Veta Pass west of Walsenburg, somewhat gradual climb for a bit then a gradual drop down into the San Luis Valley. The vistas of the mountains are breathtaking as you come down off La Veta; Blanca Peak, Mt. Lindsey and Slide Mountain all visible to the north of the highway, in stark contrast to the agricultural fields throughout the valley. If you get a chance, a side trip to the Great Sand Dunes National Park would be something you won't see anywhere else -- sand dunes butting up against 14000 ft mountains. Worth a stop.
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