The Gadsden Purchase finished what the Treaty of Guadalupe Hidalgo started. The old Spanish presidio at Tucson – known affectionately to locals as the “Old Pueblo” – was declared American territory on June 8, 1854. Few noticed.
There were only 500 citizens at the time, and a scant few were white. Most Americans looked at the dusty old presidio, situated a day’s ride north of the Mexico border and surrounded on all sides by as many mountain ranges as hostile Apache war bands, and saw only a sweatbox populated by too many undesirables to make it worth their while. A more learned sort saw that, for all the danger that life south of the Gadsden line offered, Arizona was a land of unspeakable promise.