[3] On April 6, 1932, SH 80 had a planned extension south to Nixon designated.

[10] On February 20, 1940, the section from Karnes City to the Atascosa–Karnes county line was cancelled.

On March 26, 1942, the section from Wimberley to San Marcos was transferred to Ranch to Market Road 12.

On June 24, 2010, RM 12 was shifted to an alignment south of San Marcos, and the SH 80 designation was extended through the city to a terminus with RM 12 west of the city.

On January 26, 2017, the section of SH 80 from RM 12 to Loop 82 was removed from the state highway system and was given to the city of San Marcos.