Trackwork began in 1856, and a line was completed to Victoria, Texas in April, 1861, when the Civil War broke out.
Among the founders of the railroad were German-born railroad engineer Gustav Schleicher and Joseph E. Johnston who was an army officer stationed in San Antonio, who would later be a General in the Confederate army.
[1] To facilitate the construction of a railroad from the Gulf to San Antonio, the SA&MG received 735,938 acres (2,978.24 km2) of land from the State.
[2] Confederate General John B. Magruder ordered the destruction of the San Antonio and Mexican Gulf to prevent its falling into the hands of enemy forces.
On August 4, 1870, the Texas legislature authorized the consolidation of two rail lines, the Indianola Railroad Company and the San Antonio and Mexican Gulf Railroad Company, into a new corporation to be called the Gulf, Western Texas and Pacific Railway.