US 81 at its inception in 1926 followed the route of
State Highway 2 (SH 2), which began in
Laredo and passed through
San Antonio,
Austin,
Waco, and
Fort Worth before passing over the
Red River into
Oklahoma north of
Ringgold. The 1936
Official Map of the Highway System of Texas clearly shows the route labeled both as US 81 and SH 2. It was cosigned with
US 83 for from Laredo to south of
Webb, with
US 79 for from Austin north to
Round Rock, and with
US 77 for from Waco to
Hillsboro. In 1940
US 287 was extended south into Texas, and a stretch from Fort Worth northwest to
Bowie was cosigned with US 81. The summer 1941
Texas Highway Map shows this pairing, and the current southern terminus of US 81 is still cosigned with US 287. The spring and summer 1949
Texas Highway Department Official Map designates the length of US 81 from Laredo to Fort Worth as part of the
National System of Interstate Highways, but no numeric designation was given at the time. It was not until 1959 that parts of US 81 in Texas appeared on the
Texas Official Highway Travel Map cosigned with
I-35 shields. Succeeding maps reflect the slow completion of I-35 and
I-35W over the stretch of US 81 between Laredo and Fort Worth, with the 1978-79
Texas Official Highway Travel Map showing only a section from
Encinal north to south of
Artesia Wells as incomplete, and the 1980
Texas Official Highway Travel Map shows that section completed. In 1980, US 81 was cosigned with I-35 and I-35W except where the Interstate bypassed towns; US 81 provided the main route through town and then reconnected with I-35 on the other side. The longest section of US 81 in 1980 not cosigned with the Interstate ran from I-35 in Hillsboro north to I-35W, just north of
Grandview. This section of US 81 became
SH 81 in 1991 when most of US 81 in Texas was decommissioned. The section of highway from
Devine to
Lytle became
SH 132 and the section from
Derby to the
Pearsall town square became
Spur 581 when US 81 south of Fort Worth was decommissioned in 1991. ==Junction list==