Baja Arizona's prequel

Southern Arizona's bid for statehood is getting more attention than any other 51st-state effort has in recent years. The "Save our State" group founded by Paul Eckerstrom and Peter Hormel has received a lot of national press lately. So it's worth noting the history of this region... because Tucson almost didn't make it into the United States at all. Long a part of Mexico, the region south of the Gila River was the last major piece of the lower 48 to get added to the USA. Franklin Pierce sent James Gadsden down to buy up a big chunk of Mexico in 1853. The Mexicans weren't selling, but finally agreed to give up a small sliver—which is now southern Arizona (and New Mexico). Had Gadsden been more persuasive, all of Mexican Sonora, Chihuahua, and lower California would have been part of the US. That would have meant carving up the western states differently, and the Gila River would have been an excellent dividing line. Tucson likely would have been the capital of the new state of Sonora. Bottom line: Had Gadsden succeeded, Arizona's continuing north-south battle would have been solved long ago. (There's much more on this  in the book Lost States. )