My friend Doug Rippey, the University of Denver archivist, sent the following instruction on how to reach the video of the moving map year by year - you may have to give it a couple of minutes to load. It last 1 minute, 27 seconds. This is the most vital part of my post on Manifest Destiny since 1776 here and worth looking at.
The video was available at http://www.youtube.com/watch?v=pJxrTzfG2bo
last night and just now. Loads very slow via Comcast -- your mileage may vary.
The map itself, of course, is the best part.