, or '''SH 21''', runs from the
Texas -
Louisiana boundary east of
San Augustine to
San Marcos in east and central Texas.
was one of the original 26 routes proposed in Texas in 1917 along a route from St. Augustine to
Gonzales . There was proposed extension southward to Karnes City by 1922, but was not built. By 1933, the terminus was shortened to
Giddings . By 1943, the western terminus had been rerouted through Paige to end in
San Marcos , along its current route.
