C, B, L, X, T, K, O N, M, A, J, G, H, I 1st, 2nd, 3rd, 4th 5th, 6th, 7th 8th, 9th, 10th, 11th 12th, 13th, 14th, 15th, 16th ... Paradise! Let's go to Great Falls to- -day Where the streets don't start with A
The lyrics give the lettered streets and avenues of Great Falls roughly in order from the top of the hill to the Connecticut River. "Roughly" because they aren't all parallel to one another, and one is even the discontiguous continuation of another.
Legend has it that the Hurricane of '27 blew all the street signs into the air, and wherever they came to rest locals just put 'em back up. The "Miracle of Great Falls" is that the numbered street signs all landed in order.
Paradise Parkway was originally 17th Street. (This, at least, is true.)