The Southern Pacific Railroad of Mexico (reporting mark SPM) was a railroad subsidiary of the Southern Pacific Railroad in Mexico, operating from Nogales, Sonora, to Mazatlán, Sinaloa. The Sonora Railway was constructed by the Atchison, Topeka and Santa Fe Railway between 1879 and 1882. In 1898 the Santa Fe leased the Sonora Railway to the Southern Pacific in return for the latter railroad's line from Needles to Mojave, California. This arrangement continued until December 1911, when the Southern Pacific purchased both the Sonora Railway and the New Mexico and Arizona. The following June, the Sonora Railway became part of the Southern Pacific Railroad in Mexico."