[computmaxer]

That's a bit of an exaggeration - there are definitely roads checkerboarded at 1 mile intervals, but most are gravel in between some paved ones.

[sophacles]

This may vary state to state. I know that in IL it seems that well over half of them are paved, or tarred gravel. The southern end of IL has less of this tho... but the amount paved is increasing. When I was a kid visiting relatives, I learned to drive on a lot of gravel roads, but heading down there for a funeral not long ago, most of the gravel I learned to drive on is paved now.

[dredmorbius]

Paving rate varies but can be quite high. The one mile grid though is quite prevalent.