In 1959 and 1960, The Arizona Bureau of Mines – University of Arizona, predecessor to the Arizona Geological Survey published the Arizona County Geologic map series. Until now, these important maps were only available in printed form.
Over the next two weeks, The Arizona Geological Survey will release the maps online for free download. The map scale is 1:375,000 and the contour interval is 500 feet.
You can check their facebook page for release announcements:
So far AZGS has release maps for:
Apache and Navajo counties: http://repository.azgs.az.gov/uri_gin/azgs/dlio/1618
Coconino County: http://repository.azgs.az.gov/uri_gin/azgs/dlio/1620 A portion of this map is shown below.
These maps are valuable in that they give the big picture of County and State geology. For a list of all maps available for download, see: http://repository.azgs.az.gov/facets/results/maps