Atlas of the Historical Geography of the United States. This online atlas contains more than 700 historical maps of the United States. The maps within the atlas are arranged into eighteen sections. As a student and teacher of history I was drawn to the sections devoted to population, territorial expansion, political parties and elections, and military history.
Many of the maps within the Atlas of the Historical Geography of the United States can be animated to show changes over time. For example, in the section on States, Territories, and Cities you can view individual maps for each decade from 1790 to 1930 or you can click the "animate" button to see the maps put together in a time lapse animation. All of the historical maps in the Atlas of the Historical Geography of the United States are displayed on top of a contemporary outline of the United States.
Many of the maps have interactive elements. For example, in the section on Political Parties and Opinions you can click on a county or state to see how people voted in that area.
To help students understand what they are seeing on each map, the Atlas of the Historical Geography of the United States includes a text option that can be selected while viewing a map. Clicking the "text" box will display relevant information in the sidebar of the map.
Applications for Education
The Atlas of the Historical Geography of the United States is a treasure trove of resources for teachers and students of U.S. History. In looking through the maps I could see a number of activities in which students compare maps from two categories and try to develop correlations between them. For example, I might ask students to compare maps from the section on Transportation with maps from the section on Boundaries.