Rio Grande forms the Southern border of the United states.
The gulf that forms part of the southern border of the United States is the Gulf of Mexico
There are two countries that form the borders of the United States: Canada and Mexico. Canada forms the northern border of the United States and Mexico forms the Southern border of the United States.
The Rio Grande, Spanish for grand river, forms the southern border of the United States, but it only forms the border between Texas and Mexico. New Mexico is not bordered by the Rio Grande, for example, but rather the Rio Grande runs through New Mexico.The only river that partially forms the southern border of the U.S. is the Rio Grande on the Texas/Mexico border.The rest of America's souther border with Mexico is a land border in souther New Mexico, Arizona, & Colorado.
The Mississippi river forms the western border of the southern colonies.
The Rio Grande forms part of the southern border of the US, separating the United States from Mexico. It is the fourth-longest river system in North America.
The Rio Grande, Spanish for grand river, forms the southern border of the United States, but it only forms the border between Texas and Mexico. New Mexico is not bordered by the Rio Grande, for example, but rather the Rio Grande runs through New Mexico.The only river that partially forms the southern border of the U.S. is the Rio Grande on the Texas/Mexico border.The rest of America's souther border with Mexico is a land border in souther New Mexico, Arizona, & Colorado.
Arkansas
Rio Grande makes up most of the southern border of the United States, it also makes up most of the northern border of Mexico
The Rio Grande, Spanish for grand river, forms the southern border of the United States, but it only forms the border between Texas and Mexico. New Mexico is not bordered by the Rio Grande, for example, but rather the Rio Grande runs through New Mexico.The only river that partially forms the southern border of the U.S. is the Rio Grande on the Texas/Mexico border.The rest of America's souther border with Mexico is a land border in souther New Mexico, Arizona, & Colorado.
The U.S. southern border is formed by Mexico and the Gulf of Mexico.
At the beginning of the US Civil War, the "southern" border States were Kentucky and Missouri. In this answer, Maryland is excluded in that although it was a pro=southern slave State, it cannot be considered a border State.