One of the serendipitous finds of my research for the map exhibit was this map.
I bought it to show that there were Indian nations in North America before the arrival of the Europeans. When I showed it to Mike Mathes he told me why the Athabascan language is spoken in Alaska and in New Mexico.
Sometime around the year 1000 a volcano many times more violent than Mt St Helens erupted and the ash that spewed forth drove the Athabascan speakers south. They migrated all the way to New Mexico and Arizona where the Anasazi were pushed out and the people from the north became the Navajo.
These maps tell the story of an early North American migration and are one of the featured maps in the current exhibit at Cal State LA.