In the initial assignment of state highways in 1917, Dallas-Fort Worth and Houston were connected by a branch of SH 2 (SH 2, the Meridian Highway), which ran via Waco and Bryan and continued on to Galveston. The more direct route followed by US 75 was not initially part of the system between Richland (connected to Dallas by SH 14) and Huntsville (connected to Houston by SH 19). This Richland–Huntsville cutoff was added by 1919 as State Highway 32, and US 75 was assigned to the alignment, as well as SH 6 north of Dallas, in 1926. The branch of SH 2, which US 75 followed between Houston and Galveston, eventually became part of SH 6, and these numbers were dropped in the 1939 renumbering.
