Ever since Texas became a state, the Rio Grande has been the border between the U.S. and Mexico. But rivers can move — and that's exactly what happened in 1864, when torrential rains caused it to jump its banks and go south. Suddenly the border was a different place, and Texas had gained 700 acres of land called the Chamizal, named after a plant that grew in the area.

The Chamizal was a thorn in the side of U.S.-Mexico relations for a century, until Sept. 25, 1964, when the U.S. finally gave part of the land back to Mexico. But by that time, roughly 5,000 people had moved to the area and made it their home. This is their story.