Yuma Crossing
Immediately after the Mexican–American War in 1848, the U.S. Army built Fort Yuma here to protect travelers from Indians raiding the area. It was the center point of conflict in the Yuma War of 1850–53. From 1864–1890, the fort and nearby facilities was the main army base to support the US Army's efforts to control the Indians throughout the greater southwest.
Naco, Sonora
A more important confrontation took place here called the Siege of Naco. The siege was the longest sustained battle of the Mexican Revolution lasting 119 days from 1914 to 1915. The conflict directly or indirectly involved or affected all of the major players of the Revolution and affected the final outcome of the conflict. The battle was fought between forces loyal to Francisco Villa (called Villistas) and forces loyal to the Constitutionalist faction of Venustiano Carranza and Alvaro Obregón. The battle was prompted by Governor José María Maytorena’s decision to challenge Constitutionalist forces under command of Plutarco Elías Calles in Sonora for control of this state in the fall of 1914. Maytorena’s forces attacked Calles’ forces in Nogales and forced them to retreat to Naco. Here the Constitutionalists dug in and Maytorena began a siege, trying to overrun Naco’s defenses for nearly four months. The protracted conflict claimed heavy losses on both side and property damage to Naco, Arizona, prompting fears of US citizens violating federal neutrality laws. Extra troops were sent to nearby Fort Huachuca to protect U.S. interests, with cavalry regiments placed along the border to make sure the fighting did not spill across it. This resulted in several cavalry soldiers being wounded by stray bullets. U.S. Army Chief of Staff Hugh L. Scott was sent to broker a truce, and succeeded with the signing of the Treaty of Naco on 15 January 1915.