I know lots of my friends and contacts also like to wander around the back roads of the American west, and a couple of years ago I found a resource that may be of interest. The US Geological Survey has put all(!) of their topographic maps online, available for free download as .pdf files. Here's the main URL:
store.usgs.gov/b2c_usgs/b2c/start/%28xcm=r3standardpitrex_prd%29/.do
Click on the "map locater" in the upper left corner. They've included, not just all versions of the current map series (7.5', 30x60', etc., in all different revisions by date) but also obsolete series going back to the 1880s! It's kind of a kick to check out the differences in the areas covered over the years. Of course, the early maps weren't made from air photos, either, and you get a sense that some of the surveyors were much better than others!