Impressive!!! A New Reference Resource: USGS Historical Topographic Map Explorer

Released right before the 4th of July by the USGS and ESRI. This is one cool and impressive tool!!!
Details from the News Release:

Two of the nation’s most authoritative mapping sources, the U.S. Geological Survey and Esri, have partnered to put the rich tapestry of U.S. Historical Maps into the hands of everyone. Available in time for the Fourth of July and able to be accessed on all digital devices, the USGS Historical Topographic Map Explorer brings to life more than 178,000 maps dating from 1884 to 2006.
In the past, the USGS historical maps were available only as printed lithographic copies. More recently, the legacy quadrangles were made available as free, downloadable GeoPDF versions as part of the USGS Historical Topographic Map Collection. The USGS Historical Topographic Map Explorer application allows users to access the historical maps as high resolution georeferenced images for use in web mapping applications, and features a timeline to easily select the desired maps.
Using the app is quite simple:

1. Go to historicalmaps.arcgis.com/usgs/ (no need for a download from an app store)
2. Find/search the place of your choice and click on the map.
3. Select maps in the timeline.
4. Move the slider bar to see the changes over time.
5. Share it with friends.
6. Save a copy of the maps to your desktop.

[Our emphasis] Later this month, the app will be available in GitHub, allowing the GIS community to create their own scanned and geo-referenced collection, configure the app, and see these digital collections come to life.

The USGS Historical Topographic Map Collection was officially launched on September 12, 2011.
Direct to USGS Historical Topographic Map Explorer
See Also: More than 90,000 USGS Historical Topographical Maps Now Online (September 12, 2011)

Filed under: Digital Collections, Interactive Tools, Maps, News, Patrons and Users