The Rio Grande River, defining 3,141 Kilometers (1,952 miles) of the border.
Rio Grande
The border
It is the southern border for Texas; conversely, it is the northern border for Mexico.
An artificial boundary is a boundary made by humans, examples include dams, the fence at the border between the U.S and Mexico. A natural boundary is a boundary made by nature, a boundary that "happens" naturally, examples include rivers, mountains and such.
A natural boundary is a separation of land made naturally, such as the Himalayas separating the Indian subcontinent from the rest of Asia. A political boundary is a land made separation of land, such as the United States-Mexico border.
The Rio Grande acts as a natural border between Texas and Mexico.
Both "imaginary lines" as well as a natural border, conformed by the Rio Grande River.
The Rio Grande (Rio Bravo, as known in Mexico) qualifies as the current natural border between the U.S. and Mexico.
The Rio Grande river is a part of the border between the US and Mexico.
The natural border between Asia and Europe are the Ural Mountains and the Caucus Mountains.
The Rio Grande River (Rio Bravo as known in Mexico) forms a natural boundary between the southwestern United States and Mexico; however it is not a waterway as the river is not navigable.
A short stretch of the Rio Grande River serves as the boundary between Texas and New Mexico.