U.S. Route 80 (also known as U.S. Highway 80 and US 80) is a U.S. highway that begins in the state of Texas in Dallas at an interchange with I-30. US 80 runs in an east–west direction for most of its length from Dallas to Louisiana. Before the advent of the Interstate Highway System, US 80 through Texas was once a vital link in a major transcontinental highway with the national western terminus being in San Diego, California rather than Dallas. Since 1991, most of US 80 in Texas has been decommissioned in favor of I-10, I-20 and I-30 between the New Mexico state line and its current western terminus.