Mexico–United States international park
The Mexico–United States international park, also known as El Carmen Big Bend Complex, is a proposed transboundary protected area straddling the part of the U.S.–Mexico boundary delineated by the Rio Grande. Proposed by U.S. President Franklin Delano Roosevelt to Mexican President Manuel Ávila Camacho in 1944, the goal remains unfulfilled.
Source: Wikipedia — Mexico–United States international park (CC BY-SA 4.0)