Hmm, this makes feel like I was supposed to have noticed something with the altitude on my drives through Colorado...
Yep, and not only for the fact that it's high, but it's actually the highest point on the U.S. Interstate Highway system.
But the reason you didn't notice it, is either cuz you simply do not feel it (if you're not pregnant, or sick) when the only thing you do is pressing a gas pedal...
Or - the more likely scenario - that you were blown away by the breathtaking engineering that the I-70 has to offer, that you simply didn't realize the sudden drop in oxygen