In 1932, Charles O. Paullin and John K. Wright published Atlas of the Historical Geography of the United States, a reference of almost 700 maps about a varied set of topics, such as weather, travel, and population. The Digital Scholarship Lab at the University of Richmond brought the atlas to digital life.
In this digital edition we've tried to bring—hopefully unobtrusively and respectfully—Paullin and Wright’s maps a bit closer to that ideal. First, with the exception of the historical maps from the cartography section and a handful of others (those that used polar projections, for example), we’ve georeferenced and georectified all of the maps from the atlas so that they can be overlaid consistently within a digital mapping environment. (Georeferencing is a process of linking points on a map to geographic coordinates, and georectification is a process of warping a map using those coordinates to properly align it within a particular projection, here web mercator.) High-quality scans of all of the maps as they appeared on the plates are available too.
Not only are the maps overlaid on a slippy map, but the lab also added simple interactions with tool tips and animation so you can look more specifically at the data.
I could spend all day (or several days) looking through this. [Thanks, Lee]