Check out these image websites images:
The sun sets over the mountains
Image by Stuck in Customs
I checked the sweet internet earlier in the day to see exactly what time sunset was in Yellowstone. I have the sunrise/sunset website bookmarked, which is kinda strange, maybe... Anyway, It said 7:03 or something like that. I knew full well that it means the exact moment when the sun dips below the horizon, so the sun really "sets" about 30 minutes before that... but that didn't help me get into the right position to see the sun right before it dipped below the mountains.
Luckily, there was a fine band of yellow sky lit up above the mountains, reflecting across the Madison River.
from the blog at www.stuckincustoms.com