The USGS National Geospatial Program (NGP) is converting historical printed topographic quadrangles to an electronic format (GeoPDF). This scanning and processing effort serves the dual purpose of creating a master catalog and digital archive copies of the irreplaceable collection of topographic maps in the USGS Reston Map Library as well as making the maps available for viewing and download from the USGS Store. The loading of the more than 200,000 historical maps to the USGS Store has begun, and there are currently 90,000 GeoPDF maps available to download and view.
No Arizona maps have been added to the archive yet. [right, 1961 Baynesville, KS, 1:24,000 quad]
[taken in part from the USGS news release]