An article (http://www.usends.com/blog/history-along-the-westernmost-segment-of-us-34) that dives deep into historic alignments, current signposting, and more about the Colorado segment.
Thanks your east story is interesting too. I think the break at Sheffield makes more sense post 80. It saves about 12 miles over 74 and 110.
Illinois includes the 47 to Chicago and Galesburg Burlington in the NHS The rest is FAS.