I watched this YT video [1] about the interstate system recently, I found it informative and entertaining

To me, the Eisenhower Tunnel in CO [2] is noteworthy. It crosses the continental divide at altitude. From what I've read and watched, they don't allow HAZMAT trucks to go through, because the risk is simply too high (well equipped fire/rescue departments are hours away, among other factors)

[1] https://www.youtube.com/watch?v=SR7BA3xEmDo

[2] https://en.wikipedia.org/wiki/Eisenhower_Tunnel?useskin=vect...