SH 48 was originally designated on August 21, 1923, from
Daingerfield east through
Linden to
Atlanta as a renumbering of a portion of
SH 1A. On June 24, 1931, this route was redesignated as a rerouting of
SH 47.
SH 48 was instead designated on that same day from
Pharr through
Harlingen to Brownsville, along the current route of
U.S. Highway 83. On November 30, 1932, it was extended west to
Mission, replacing part of
SH 4. On January 19, 1935, this route was swapped with SH 4, which ran closer to the
Rio Grande along Military Highway, and was extended east out of the city to the Port of Brownsville. On September 26, 1939, it was replaced an extension of
SH 107 from Mission to Hidalgo and
US 281 from Hidalgo to Brownsville, so that only the section from Brownsville to the port was left. On October 28, 1973, SH 48, was signed to
Port Isabel along
Farm to Market Road 1792. On August 26, 1990, it was officially extended over
Farm to Market Road 1792. ==Major intersections==