Sonora

From Turtledove

(Note this picture is pre-Great War as part of it was annexed to the U.S in 1918)

Sonora is a state of the Confederate States, bought from Mexico with Chihuahua for $3,000,000 in 1880. The purchase of Sonora and Chihuahua was the casus belli for the Second Mexican War. Part of it was annexed by the United States after the Great War. Sonora is the home of the only Confederate Pacific port, Guaymas.