[1] "OSR" is the only state highway in Texas with a completely alphabetical designation and one of only two where the designation begins with a letter (Texas State Highway NASA Road 1 being the other with a beginning letter).

It crosses U.S. Route 190 (US 190) / Texas State Highway 6 north of Bryan.

On March 26, 1942, a section from US 81 (now I-35) in San Marcos east 4.4 miles (7.1 km) was added (creating a gap), and the designation was changed to SH OSR.

On August 2, 1943, the section from SH 29 to 4.4 miles (7.1 km) east of San Marcos was added, closing the gap.

[1] Media related to Texas State Highway OSR at Wikimedia Commons