State Highway 45 was originally designated on August 18, 1919, as a route from
Bryan to the
Louisiana border. On September 17, 1923, the section west of
Roans Prairie was cancelled. On August 11, 1925, SH 45 was rerouted through Point Blank, Coldspring and Shepherd. On March 19, 1929, a branch of SH 45 on a more direct route from Point Blank to Livingston was designated. As of March 19, 1930, large portions of the highway were still under construction along the proposed route. The section of the branch from Point Blank to Coldspring was renumbered as
SH 156 and the section of the branch from Coldspring to Shepherd was renumbered as part of SH 150, so that SH 45 went on the most direct route between Point Blank and Livingston. By 1938, the road was complete, with small portions remaining as a dirt road. On September 26, 1939, the highway from
Huntsville to Jasper had been transferred to
U.S. Highway 190, the stretch from Jasper to the Louisiana state line transferred to
SH 63 (this was originally proposed as
SH 296, and the section from Roans Prairie to Huntsville redirected north to
Crockett. on August 24, 1960, the stretch from Huntsville to Crockett was transferred to
SH 19. On December 15, 1960, the rest of SH 45 was canceled and transferred to
SH 30 to avoid confusion with I-45. The current route was designated, but not constructed, on May 22, 1985, as a proposed Austin Loop, along with
SH 130 (north of US 183 only). SH 45A was a spur designated on September 14, 1926, from Coldspring west to New Waverly. On March 19, 1930, this spur was renumbered as
SH 150. On February 11, 2021, icy conditions caused a 26 vehicle pile-up. This incident occurred near the overpass with
RM 620. Three people were hospitalized. The interchange at
I-35 was partially affected by the
March 21, 2022 tornado outbreak when a large light pole was ripped off its foundation, the debris resting on the side of a flyover, as seen from photos captured by
KXAN-TV. ==Exit list==