The St. Louis Southwestern Railway Company of Texas operated that part of the St. Louis Southwestern Railway system located in Texas. The company was chartered on January 12, 1891, to acquire the properties formerly operated by the St. Louis, Arkansas and Texas Railway Company in Texas, which were sold under foreclosure on January 9, 1891. The Texas company was owned by the St. Louis Southwestern Railway Company, commonly called the Cotton Belt, but operated separately in conformity with Texas law. Historically, the Cotton Belt main line ran from St. Louis and Memphis on the east through Texarkana to Dallas/Fort Worth and Gatesville on the west. Including branch lines, on June 30, 1915, the system owned 1,542 miles of main track, of which 803 miles were in Texas. The St. Louis Southwestern also operated over an additional 230 miles via trackage rights. The business office of the St. Louis Southwestern Railway Company of Texas (Southwestern of Texas) was located at Tyler, and the initial capital was $15,000,000. Members of the first board of directors included Louis Fitzgerald, Edwin Gould, and Winslow Pierce of New York; George Clark and C. M. Shelly of Waco; S. W. Fordyce of St. Louis; Tom Randolph of Sherman; J. A. Edson of Tyler; H. G. Fleming of Texarkana; and James Garrity of Corsicana. The Southwestern of Texas acquired 553 miles of main track extending from Texarkana to Gatesville with branches from Mount Pleasant to Fort Worth, Commerce to Sherman, and Corsicana to Hillsboro. This mileage had been built by two predecessor companies beginning with the Tyler Tap Railroad Company, which opened between Tyler and Big Sandy on October 1, 1877. Following a name change to the Texas and St. Louis Railway Company, the line built between Texarkana and Big Sandy and from Tyler to Corsicana. The railroad was renamed the Texas and St. Louis Railway Company in Texas. Under this name the track between Corsicana and Gatesville was completed. The 305 miles of track between Texarkana and Gatesville was acquired by the St. Louis, Arkansas, and Texas Railway Company in Texas, which built the lines to Sherman, Fort Worth, and Hillsboro. The Southwestern of Texas, on October 6, 1899, merged the Tyler Southeastern Railway Company, operating ninety miles from Tyler to Lufkin, and on July 7, 1903, acquired the twenty-two miles of the Texas and Louisiana Railroad Company, running from Lufkin to Monterey. The company began serving Dallas via trackage rights in 1896 and in 1903 built its own twelve-mile line between Addison and Dallas. It completed four miles between Monterey and Warsaw in 1904 and on September 14, 1907, bought sixteen miles of railroad between Warsaw and White City from the Lufkin Land and Lumber Company. This gave the company 697 miles of main track. The Southwestern of Texas also owned a one-eighth interest in the Union Terminal Company at Dallas. Abandonment of Texas branch lines began 1933 with the thirty miles between Prestridge and White City, followed by the twelve miles between Lufkin and Prestridge in 1939. The following year the Hillsboro branch was abandoned, the Sherman line in 1953, and the line between Addison and Dallas in 1965. Trackage rights over other railroads were substituted in order to continue service to several markets on the abandoned lines. The western end of the original main line between Gatesville and Lime City was abandoned in 1972. The Southwestern of Texas owned its locomotives and cars jointly with the St. Louis Southwestern, with the Texas line owing a 40 percent interest in the equipment. In 1928 this included 250 locomotives, 9,642 freight and company service cars, and 172 passenger cars. Revenues in Texas that year were $554,212 for passenger and $6,385,674 for freight.
The St. Louis Southwestern owned three other railroads in Texas, two of which were subsequently abandoned. In 1910 it acquired the Stephenville North and South Texas Railway Company operating between Stephenville and Hamilton and extended the line from Hamilton to Gatesville and from Edson to Comanche for a total of 106 miles. This company was leased to the Southwestern of Texas on July 1, 1913. The tracks between Hamilton and Stephenville and from Edson to Comanche were abandoned in 1934 and the balance of the railroad in 1941. The Eastern Texas Railroad Company running between Lufkin and Kennard was acquired in 1906 and was operated as a separate company. This line closed in 1921 and was formally abandoned in 1924. The Dallas Terminal Railway and Union Depot Company was acquired in 1901 to provide terminal facilities at Dallas. This company was merged into the Cotton Belt in 1994.
The Southern Pacific Company gained control of the St. Louis Southwestern system on April 14, 1932, but the Cotton Belt continued to be operated separately. The Southwestern of Texas was leased by the St. Louis Southwestern on March 1, 1954, and merged into the parent company on January 19, 1984. The St. Louis Southwestern doubled its size in May 1980 when it began operating the former Chicago, Rock Island and Pacific Railroad Company track from Tucumcari, New Mexico, through Dalhart to Kansas City and St. Louis. This trackage, part of the Golden State Route, was subsequently purchased from the estate of the Rock Island. In 1992 operations of the Cotton Belt were consolidated with those of the Southern Pacific Transportation Company.