U.S. Route 77 (US 77) is a major highway that is part of the United States Numbered Highway System that runs from the Veterans International Bridge in Brownsville to Sioux City, Iowa. In Texas, the road runs south-north for 471.3 miles (758.5 km) from the International border with Mexico to the Oklahoma state line north of Gainesville. The highway is being upgraded to a freeway near Corpus Christi to connect to the freeway part of the highway in Raymondville as part of future I-69. A freeway in Robstown is already signed as part of I-69. From Waco to the Oklahoma state line, US 77 overlaps or runs parallel to I-35/I-35E.

Harlingen is a city in Cameron County in the central region of the Rio Grande Valley of the southern part of the U.S. state of Texas, about 30 miles (48 km) from the coast of the Gulf of Mexico. The city covers more than 40 square miles (104 km2) and is the second-largest city in Cameron County, as well as the fourth-largest in the Rio Grande Valley. As of the 2020 census, the city had a population of 71,892.