Sonora had been a Mexican province during the early 19th century. Most of the problems they faced were with the local Apache, whom many northern residents distrusted and hated. In 1881, the Empire of Mexico was bankrupt and in order to pay its creditors, sold the provinces of Sonora and Chihuahua to the Confederate States for three million dollars. This triggered the Second Mexican War, but the province saw no action as the CS Army chose to take the fight to the enemy rather than sit and wait for
them. Upon the successful conclusion of that campaign, tensions between the local Mexicans and Apache Indians exploded into violence, which the CS Army had to suppress.
In the following years, Sonora represented the very fringe of the Confederacy as it connected the CSA from the Atlantic to the Pacific with the transcontinental railway, that terminated at the major port city of Guaymas. Sonora's economy was mainly fuelled by copper mines and trade with the Pacific Ocean. During the 20th Century, the Great War brought war to the state when the US Army invaded in 1914. Unlike the blood and mud of trench warfare back east, fighting out in the province was scattered and mobile. Still, in spite of the valiant defence put up by the defenders, the US Army pushed them back, annexing a chunk of northern Sonora into New Mexico. These areas contained valuable copper mines, though in the aftermath of the war, many copper kings were still thriving in spite of the damaged economy.
During the Second Great War, in 1943, the US attacked and occupied the Mexican province of Baja California, and closed off the Pacific to the CS Navy. The next year, the war ended and the entirety of Sonora, along with all other Confederate states, was occupied by the USA.