|Auxiliary route of US 81|
|Length||136.76 mi (220.09 km)|
|South end||/ at Corpus Christi|
|North end||near San Antonio|
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.
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.
Immediately after Portland is Gregory, where US 181 and TX 35 splits, and the freeway portion of US 181 ends. SH 35 proceeds eastbound to Aransas Pass and Rockport while US 181 proceeds northwest towards Taft and Sinton. US 181 shares a duplex with SH 188 and US 77 Business in Sinton, and makes a right turn at San Patricio Street, proceeding northbound.
North of Sinton, US 181 passes through the towns of St. Paul, Papalote, and Skidmore, before reaching Beeville. US 181 business runs through downtown Beeville while drivers passing by can use the US 181 freeway bypass on the east side of town. In Beeville, US 181 intersects with US 59 (Future I-69W) (northbound to Victoria/Houston & southbound to Laredo).
North of Beeville US 181 passes through a number of unincorporated towns including Normanna, Pettus, and Tuleta before reaching Kenedy. US 181 business serves downtown while US 181 runs on the west side of town. Immediately north of Kenedy is Karnes City, where US 181 business runs parallel again east of US 181 through Karnes City.
North of Karnes City US 181 passes through Hobson (unincorporated), followed by Falls City, Poth, and Floresville. US 181 business runs west of US 181 through downtown Floresville.
North of Floresville US 181 passes through the town limits of Elmendorf before intersection with State Loop 1604 (Anderson Loop, surrounding San Antonio), and ends 8 miles north at its northern terminus at I-37, just south of I-37 and I-410 on San Antonio's far south side.
US 181 is one of the original routes accepted by AASHO in November 1926. Its original southern terminus was at a junction with its parent, US 81, and US 90 in Downtown San Antonio. By 1968, the portion between Downtown and Loop 13 had been removed from the state highway system. The completion of I-37 in San Antonio during the 1970s resulted in the truncation of US 181 to its interchange with that freeway; the segment north of this point along Presa Street was transferred to Spur 122.
|Nueces||Corpus Christi||to to / Shoreline Boulevard / Broadway Street - Bayfront, Corpus Christi Museum, Airport, San Antonio, Chapman Ranch, Robstown||south end of freeway; south end of SH 35 concurrency|
|Tancahua Street / Staples Street||Southbound exit and northbound entrance|
|Port Area||Southbound exit and northbound entrance|
|Corpus Christi Harbor Bridge over Corpus Christi Channel|
|Burleson Street - Corpus Christi Beach|
|Beach Avenue - Corpus Christi Beach|
|Nueces Bay||Nueces Bay Causeway|
|San Patricio||Portland||Indian Point Park|
|Frontage Road||southbound access only|
|(Moore Avenue) - Taft||no direct southbound exit (signed at FM 2986)|
|(Wildcat Drive) - Sinton|
|Lang Road||southbound exit only|
|(Buddy Ganem Drive) to / Northshore Boulevard|
|||La Quinta Terminal||northbound access only|
|Gregory||north to south - Aransas Pass, Rockport, Houston, Port Aransas||interchange; north end of freeway; northbound exit and southbound entrance; north end of SH 35 concurrency|
|north - Woodsboro|
|||To south / north (via Spur 202 / FM 2986) - Ingleside, Port Aransas, Aransas Pass, Houston||interchange|
|Taft||east||South end of FM 631 concurrency|
|west (Davis Road) - Odem||South end of FM 631 concurrency|
north / east to / - Rockport, Refugio, Beeville
|South end of SH 188 concurrency|
|south (Sodville Avenue)|
north (Vineyard Avenue) - Calallen, Corpus Christi
|South end of US 77 Bus. concurrency|
south (San Patricio Street) / west (Sinton Street) - Mathis, Victoria
|North end of US 77 Bus. and SH 188 concurrencies|
/ - Corpus Christi, Calallen, Victoria, Refugio
|interchange; U.S. 77 is the future Interstate 69E|
|south - Refugio, Rockport, Gregory||interchange|
|Bee||Skidmore||west to - Mathis, Alice, Lake Corpus Christi State Recreational Area|
|west (Main Street)|
north - Kenedy
|interchange; south end of freeway|
|||Emily Drive south||northbound exit only|
|||- Refugio, George West|
|Beeville||(Future I-69W) - Laredo, George West, Victoria, Goliad||U.S. 59 is the future Interstate 69W|
|||south - George West, Sinton|
|||(Charco Road)||interchange; north end of freeway|
south - Sinton
|Tuleta||west to - Mineral|
|Tulsita||west - Pawnee|
|Karnes||||north to west to west - Kenedy, Pettus|
|Green||north - Kenedy|
|||east (Allen B. Polunsky Drive) - John B. Connally Jr. Unit|
north to - Karnes City, Pettus
/ east - truck route to SH 239 east / FM 792, Three Rivers, Goliad, Cuero
|south end of SH 72 Truck overlap|
|/ east - Three Rivers, Goliad, Cuero||north end of SH 72 Truck overlap|
|east to - Helena|
south - Pettus
|Karnes City||north / north (US 181 Bus. north) - Seguin, Floresville, San Marcos, Luling|
|- Coy City, Peggy, Whitsett|
south / west - Floresville, Peggy
|Hobson||east - Panna Maria, Runge||South end of FM 81 concurrency|
|west||North end of FM 81 concurrency|
|Falls City||west (West Maverick Street) - Campbellton|
|west to - Campbellton||South end of FM 887 concurrency|
|east - Pawelekville, Gillett||North end of FM 887 concurrency|
|Wilson||Poth||to - McCoy, Kosciusko|
|north to - Stockdale|
|||east - Stockdale|
|||north (Sgt. Hugo Lange Loop) - Floresville Business District, Pleasanton, San Antonio|
|Floresville||west (Hospital Boulevard) to - Pleasanton, Jourdanton||South end of SH 97 concurrency|
|east / west (Standish Street) to - Stockdale, Espey||North end of SH 97 concurrency|
|||south (Sgt. Hugo Lange Loop) - Floresville Business District, Pleasanton, Karnes City|
|Calaveras||- La Vernia|
|Bexar||||(Anderson Loop) - Elmendorf, Converse||interchange|
|||CPS Energy Calaveras Power Station||interchange|
|San Antonio||north (South Presa Street)|
|north - San Antonio||I-37 exit 132|
|1.000 mi = 1.609 km; 1.000 km = 0.621 mi|
US 181 has business routes in Beeville, Kenedy, and Karnes City. The routes are previous alignments of US 181 through these cities, and were previously designated in the state highway system with other route numbers. The designations were changed to Business US 181 by TxDOT in 1991. A de facto fourth route, along a former alignment through Floresville, is designated Loop 181.
Business US 181 in Beeville travels through central Beeville while mainline US 181 uses a freeway bypass to the east of the city. It is officially designated by TxDOT as Business US 181-J, and was designated as Loop 516 on May 31, 1973 (which was signed as a business route of US 181), but was changed to Business US 181-J on June 21, 1990.
Business US 181 in Kenedy travels through central Kenedy while mainline US 181 passes to the west of the city. It is officially inventoried by TxDOT as two separate routes, with a discontinuity at SH 72.
Although not officially concurrent with SH 72, the signage in the area directs traffic from one segment to the other, effectively completing the loop.
Business US 181 in Karnes City travels northward and then westward through central Karnes City while mainline US 181 skirts the southwestern edge of the city. It is officially inventoried by TxDOT as two separate routes, which connect at the intersection with SH 80 / SH 123 in the east side of the city.
US 181's former alignment in Floresville is inventoried as Loop 181 by TxDOT. The route was designated on October 15, 1946 when US 181 was realigned to the east. The route begins north of the city limits; within the city, it has a brief concurrency with FM 536 and intersects SH 97 before rejoining US 181 in the southeastern section of the city.