Amarillo to Groom TX: 58.0 miles
Our hotel in Amarillo was very accommodating of our bikes, storing them for us in a large first floor storage room. (And the rooms included buffet dinner and breakfast).
Amarillo has a wonderful bike path, a rails to trails conversion. This one is actually nicer in construction than the one we experienced in Oklahoma City, but not as scenic nor, alas, as long. And when the Amarillo trail ended, we ended up pretty much off track out of airspeed, altitude, and ideas. But the trail was great.
I know pictures of wind turbines are getting repetitive, but there is a certain stark beauty both physically and in terms of engineering elegance. 
R66 began to divert from I40 and traversed in the midst of the turbine farms. The wind was strong so one could see the blades curving backward by the aerodynamic loading and hear them carving the air.
The old and new shared the wind. The old windmills had an elegant purpose, namely to pump up water from the vast Oglala underground water resource to store in tanks for later use for feedstock watering and perhaps even irrigation. This worked extremely well because the value provided did not require 24 by 7 operating conditions. The new generation turbines are generating electricity, which end use absolutely requires 24 by 7 supply. So the turbines must interface with an electrical grid where it supplements the base load power provided by, ahem, necessary (and wonderful) fossil and nuclear fueled power plants.
The wind can be useful, and it can ‘retire’ structures no longer able to withstand force and time.
Day 6 here: