Possible Clues:

• Texas town of song
• City west of Corpus Christi
• Rio Grande Plaza locale
• Town in many Westerns
• Texas city made of three notes?
• City at the north end of the Gateway to the Americas International Bridge
• Home of Texas A&M International University
• Texas city in a cowboy song
• Capital of the short-lived Republic of the Rio Grande
• U.S.-Mexico border city