The USGS has announced a schedule for release of over 100,000 historic topographic map quadrangles covering 32 states by the end of 2011. This is an amazing resource for anyone interested in studying the history of an area in the United States.
Kansas is the first state in the release schedule and it looks like historic maps for Kansas, Iowa, and perhaps several other states are already available from the USGS Store. The historic topographic maps include scales ranging from 1:24,000 to 1:250,000 and typically date back to the late 1800s or early 1900s for any given area.
Each map is a single GeoPDF, which is great for consumers, although I would personally prefer GeoTIFFs. To get the coordinate information to show up on the PDF, you must install the free GeoPDF Plugin for Acrobat, which is a bit of a hassle since you have to register and then add a 37 megabyte plugin to Acrobat. However, it is great to see that the USGS went through the extra trouble of georeferencing the maps as that makes them much more useful. The scan quality is very good. The map I looked at was scanned at 2 meters per pixel with a moderate level of compression. Although I’m not sure if they are all scanned at that resolution.
The release schedule and more information about this project can be found at the USGS National Map Historic Quadrangle Scanning Project.