http://www.orgsites.com/wi/aztalan/_pgg8.php3
Aztalan is a State Park near Lake Mills, WI. Some archeologists argue that the population moved from WI to Mexico City where they became the Aztecs. IOW, migration was the opposite direction of what we generally were taught — north to south.
I’d argue that it didn’t move either way; but if I had to argue one against the other, I’d go with the south to north idea, based on the simple fact that the ruins there are older, in fact, much older. The Aztecs were relatively late, and their language was/is related to Navaho, but the Navaho didn’t move south, they moved north.