I think that it's the Rio Grande, but I'm not positive.
Rio Grande!
The Suez Canal marks the border between Asia and Africa.
The parts of the border that are not in the Rio Grande or the Colorado River are marked by a series of monuments.
The river that flows from the Texas panhandle by the border of Louisiana is the "Red River." There is also a river in the northwestern states also called the "Red River," but don't get confused.
The Great State of Texas.
Type your answer here... texas
The Colorado River forms the border between Arizona and California and between Arizona and Nevada.
The Continental Divide marks the eastern border of the Ute reservation.
Naakáí dinéʼiʼ "Person from Mexico" Naakáí means Mexico. The marks above the vowels are high tone marks. The mark between the e and i is a consonant called a glottal stop.
Iguazu Falls marks the border between Brazil and Argentina.
The Huang He River marks the eastern border of China's Shensi province. The Danube River helps form the border between Romania and Bulgaria.
The 42nd parallel forms the southern boundary of Idaho. It marks the border between Idaho and Nevada as well as a portion of the border between Idaho and Oregon.