When you cross the Gila River in Arizona, do you realize that you’re crossing the first Arizonan border between the US and Mexico?
The Treaty of Guadalupe Hidalgo ended the Mexican-American War in 1848. While much of Arizona became US territory, the area south of the Gila River — all the way from Yuma to the New Mexico Border and including Tucson — was still disputed.
It took the US Ambassador to Mexico James Gadsden’s negotiation to purchase the land, which our nation wanted for a southern transcontinental railroad, at a cost of $10 million — equivalent to $230 million in today’s money.
– Staff Report, The Arizona 100