The routing between Madisonville and Navasota was originally set before the state's highway system was started. By 1919, a rail route between the cities existed, run by the
Great Northern Railroad. By 1922, a basic highway had been built between the cities (designated October 20, 1919 from Buffalo southwest via Jewett and Normangee to Navasota; rerouted on July 20, 1920 to the Madisonville to Navasota route), which was designated as State Highway 32A, which branched off the main State Highway 32 in Madisonville. On August 21, 1923, the state roads department had begun to get rid of most suffixed spur routes, so this route was again renumbered as State Highway 90. By 1926, it extended to Brenham, replacing a portion of
State Highway 105. The route remained a minimally serviced dirt road until the early 1930s, when paving occurred. Numerous reroutings occurred during the next 70 years, including being rerouted away from the town of
Washington on February 24, 1953 (the old route through Washington was redesignated as
FM 912) and the eventual transferral of the section between Brenham and Navasota back to State Highway 105 on February 28, 1973. On April 18, 1985, SH 90 was rerouted over
Spur 174 to
US 75, with the old route north to SH 21/US 190 becoming part of Spur 174. ==Route description==