Trivia: What river serves as the border between Texas and Mexico?
Correct Answer: Rio Grande
So why is this answer correct? : The fifth-longest river in the U.S., the Rio Grande forms the border between northeastern Mexico and the southern United States. The river begins in the San Juan Mountains of Colorado and flows south through New Mexico until it reaches Texas, where it forms the state’s southwestern border. The river also flows through Big Bend National Park, the largest national park in Texas.