Fifty years ago, the United States shrank by a single square mile. It all happened where the Rio Grande divides El Paso and Ciudad Juárez in Mexico.
Ever since Texas became a state, the river has been the border between the two countries. 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 in a different place, and Texas had gained 700 acres of land called the Chamizal (pronounced chah-mee-ZAHL), so named for a type of plant that grew there.