I have lived in four states:
Of these four states, I believe Pennsylvania has the best route shield. Pennsylvania is the keystone state (if you don’t understand why, look at a map of the original 13 states), and so it’s fitting that the route shield looks like a keystone. Distinctive and legible—good qualities in a route shield.
I like the Minnesota route shield. The colors are nice. I also like the small outline of the state in the corner. One issue is that it’s kind of hard to read the “Minnesota” from far away, but you don’t really need to, given that this shield is so distinctive.
The route shield of my home state of Oregon leaves something to be desired. It’s not very distinctive: it looks very much like all the other states that use a circular or vaguely oval-like pattern. When I was a child, I thought this route shield was some sort of deformed oval, like the default oval used for state highways on maps, until I realized it’s supposed to be the state seal. Except, with three-digit highways, they have to distort the seal to make it wide enough. I’m not saying Oregon should change its route shield—that would be a waste of money—but it’s really sad that such a beautiful state has such a drab route shield.
Sorry, but I don’t like Illinios’s route shield. It’s extremely boring and undistinctive. Worse, it looks too much like a speed limit sign!