My son Ryan sent me a link to a really unusual, but apparently very useful, website. it is called the Atlas of the Historical Geography of the United States. Here is the description from the website:
Here you will find one of the greatest historical atlases: Charles O. Paullin and John K. Wright's Atlas of the Historical Geography of the United States, first published in 1932. This digital edition reproduces all of the atlas's nearly 700 maps. Many of these beautiful maps are enhanced here in ways impossible in print, animated to show change over time or made clickable to view the underlying data—remarkable maps produced eight decades ago with the functionality of the twenty-first century.In addition, most of the maps in the atlas have been georectified, warped so that they can be placed consistently on top of a digital map. Since historical perspective is usually missing with many genealogical researchers, these types of aids can help more of us become aware of the some of the geographic factors that shaped the United States throughout our history.