The route immediately encounters its only intersection between its termini, at FM 1218, which runs just inside the state line.

[3] SH 128 was originally designated on May 21, 1927 along a route from Sinton northeast to the Victoria County line.

[6] On June 24, 1931, it had been extended west to Alice, replacing a portion of SH 12A.

[12] The current route was originally designated on May 7, 1948 as Farm to Market Road 781 and ran from the state line to FM 703.

[13] The highway was signed, but not officially designated, concurrently as SH 128 beginning on March 30, 1955, "for guidance of traveling public" to correspond with New Mexico State Highway 128 (which was renumbered from NM 256 to NM 128 that day; FM 703 was signed but not designated as part of SH 115 in October 1952).