The rolling green hills of SW Wisconsin and NE Iowa are beautiful; a perfect way to start the trip from Wisconsin to Colorado.
It is easy to forget how long the Mississippi River is when you do not live near it. I crossed it many times in the South, but crossing the Mississippi in Northern Iowa took me by surprise.
The green hills eventually subsided to green corn fields which progressed to brown corn fields; signs of the very hot and dry summer.
Driving I-5 in California, I pass a lot of trucks hauling onions, but in Iowa I passed trucks hauling parts of wind turbines. Looking up from the highway at wind farms, the turbines seem huge, but only when you pass by a blade riding along the interstate do you realize how truly enormous theses engineering masterpieces are. It was daunting and breathtaking to feel so small. One of the Iowa rest stops has a blade bolted to the ground so you can stand next to it and look upwards into eternity straining to see the tip.
Nebraska is a long, flat drive, but just like Texas there is also big sky; bright blue sky that goes on forever. To the west were clouds that looked like a long mountain range -- a Nebraska mirage. While it is easy to get lost in Nebraska's big sky, nothing beats the big sky of Texas at sunset.
(Sorry there are no pictures, but I was driving at the time and thought it might be dangerous to take my hands off the wheel to snap pictures at 70 mph.)