In antebellum Texas the increasing amount of freight arriving at Indianola and Port Lavaca destined for western markets demanded a better method of transportation than the poor wagon roads from the coast were able to deliver. Railroad entrepreneurs envisioned a number of lines to serve this market and hoped as well to tap the rich cotton-growing areas of the interior. Acting upon authorization of the state legislature, Samuel Maverick, Volney E. Howard, John C. French, Enoch Jones, John O. Meusebach, George Wilkins Kendall, Gustav Schleicher, and John J. Linn, among others, were granted a charter on September 5, 1850, which founded the San Antonio and Mexican Gulf Railroad Company. The line was to connect San Antonio and Victoria to "any suitable point on the Gulf between Galveston and Corpus Christi." All towns along the proposed route could subscribe to buy company stock to finance the project. The charter was amended in 1852 to take advantage of the new state land-grant policy for railroads, and the company was further authorized that year to intersect with the Mississippi and Pacific Railroad above San Antonio. The incorporators found it difficult to sell their stock in a state that was rich in land but lacking in powerful capitalists. The city of San Antonio and Bexar County subscribed $50,000 each in stock, but the citizens of Victoria and Victoria County stipulated that they would not subscribe to company stock until the tracks had crossed the Guadalupe River. Construction was slow and erratic, and there was disagreement over the site of the Gulf coast terminus, though the majority of the company's policy makers favored Indianola or Port Lavaca. Slow construction induced the people of Victoria and Indianola to attempt the formation of their own railroad corporations, but the two cities and their counties lacked the financial resources for lone projects.
The proposed SA&MG line continued to generate debate and competition. Indianola's attractive deeper harbor threatened Port Lavaca's chances for becoming the terminus. The city of Port Lavaca therefore offered to deepen the channel that ran to its wharves, organized the Lavaca Navigation Company, and ordered a dredge from Troy, New York. Various committees were organized in both Victoria and Indianola to consider this competition, the solutions of which included the formation of the Indianola and Guadalupe Valley Railroad Company, the Indianola and Victoria Plank and Turnpike Road Company, and the Powderhorn, Victoria and Gonzales Railroad Company, which was to build an alternative line from Indianola (Powderhorn) and bypass Port Lavaca. Although such prominent figures as Jesse O. Wheeler, Preston R. Rose, Henry Runge, David Murphree, and John J. Linn engineered these efforts, they came to nothing. Meanwhile, Enoch Jones had recruited financial backing for the SA&MG in the North, and these supporters preferred Port Lavaca as the Gulf terminus; the choice prevailed. The line was completed only to a distance of five miles from Port Lavaca by late 1857, a modest accomplishment that nevertheless prevented forfeiture of the charter and entitled the company to receive from the state 58,000 acres in land grants that could then be sold to cover construction expenses. Though the line terminated in the open prairie, it was in "constant use" and carried an "immense business," according to the state engineer's report. The development from Port Lavaca continued to worry the Indianola interests, who chartered the Indianola Railroad Company in 1858 to build a line from Indianola through Victoria and Gonzales to Austin, to connect with the Memphis, El Paso and Pacific Railroad Company. To prevent duplication of lines, however, the state required the Indianola to connect with the SA&MG track just north of Port Lavaca, at a place later called Clark's Station. By the outbreak of the Civil War the Indianola line was surveyed and graded to Clark's Station, a distance of fifteen miles, but no track had been laid; the ties were still on the docks at Indianola. The San Antonio and Mexican Gulf, suffering financial difficulties and unable to complete the last two miles of track to Victoria, was reorganized and refinanced in 1859 and completed construction to Victoria in 1860 or 1861, largely with funding from Jesse O. Wheeler. In December 1862, however, when Union forces threatened the Matagorda Bay area, Gen. John Bankhead Magruder, Confederate commander of the Texas, New Mexico, and Arizona district, ordered Maj. Daniel D. Shea to destroy the SA&MG track and the Indianola railroad ties still on the wharves. Wheeler lost his $100,000 investment upon Magruder's orders. Nevertheless, the action hindered the Union forces that finally occupied Port Lavaca and Indianola in late 1863.
In 1865–66, during Reconstruction, the federal government rebuilt the tracks from Port Lavaca to Victoria at a cost of $45,000, which was levied against the owners. Though they were unable to make the payment, the government allowed the line to continue operation. The year 1869 proved difficult, however, as extended rains weakened the roadbed enough to prevent the use of steam engines; service was reduced to triweekly and limited to light cars drawn by mules or even powered by sail. The owners, unable to secure locally the financial means to purchase the government lien and unwilling to try in the North, secured a contract with English capitalists to cover the debt, build the branch to Indianola, and extend the line into DeWitt County and even to San Antonio; but the deal fell through. In 1870 the United States government foreclosed on the property, and the stockholders, of whom John C. French was serving as president, lost their investment. The line was purchased by the steamship magnate Charles Morgan and railroad entrepreneur Henry S. McComb on May 25, 1870. Morgan had already purchased Indianola wharf properties in 1869 and was anxious to preserve his shipping interests from the threat of northern railroads building into Texas. Morgan chartered the Gulf, Western Texas and Pacific Railway Company on August 4, 1870, and on April 22, 1871, merged the San Antonio and Mexican Gulf and the Indianola companies into the new railroad. The combination was approved by the Texas legislature on May 19. The line to Indianola was completed about the end of April. However, it took until March 1873 to extend the railroad the twenty-eight miles between Victoria and Cuero.