U.S. Route 181

U.S. Highway 181 is a south–north U.S. Highway located entirely in the state of Texas. Both termini are at Interstate 37, the road that it mainly parallels to the east. US 181 begins in Corpus Christi, Texas at mile marker 0 to the south, through south-central Texas to just south of San Antonio to the north (mile marker 131), for a total length of 137 miles (220 km).

The highway's northern terminus is at an intersection with Interstate 37 one mile (1.6 km) south of San Antonio's Interstate 410 loop, about 12 miles (19 km) northwest of Floresville. Prior to the Interstate era, US 181 traveled into Downtown San Antonio along Presa St. to an intersection with its parent route, US 81, which then ran along Alamo St.

Its southern terminus is in Corpus Christi, Texas at Interstate 37 near the Gulf of Mexico. IH 37 and US 181 have mutual termini, such that traffic traveling southbound on IH 37 will automatically merge onto northbound US 181, and vice versa.

Route description

Proceeding northbound, US 181 runs through the following Texas counties: Nueces, San Patricio, Bee, Karnes, Wilson, and Bexar. At its southern terminus with Interstate 37 in Corpus Christi, TX, US 181 traverses as a freeway in the northeast direction across Harbor Bridge and the Nueces Bay Causeway, before entering Portland, TX. Past the Nueces Bay Causeway through Portland, US 181 shares a duplex with Texas State Highway 35.