Trains and Spanish Land Grants
Steve, do you like trains? On (I-8) between Yuma and Gila Bend, watch along the south side of the highway for an old round water tank (I cannot remember if it is wood or metal), but it stands on a pedestal at locomotive height and holds (or did) several thousand gallons of water -- a remnant of the steam age which the SPRR never disassembled!
After Tombstone, be sure to drive SR82 through Sonoita and Patagonia to Nogales -- this is beautiful ranch country originally deeded to Spanish nobles by the King of Spain. The Apaches made it a difficult place to live. In later years, the movie Oklahoma was filmed there. You'll be amazed how pretty it is down there.