Awesome concept for a quiz. The top two are obvious, but many of the others less so. As a west coaster, it's hard to fathom that metro area freeways in small states outweigh large western state belt freeways (Georgia? really?) Do you know if this is a tally of just freeway mileage or does it factor miles per freeway lanes? That would make it even more interesting.
BUT. there's only 50 states which means fast typers can ace this just by typing them all so you ought to consider dropping the timer a little more. just an idea.