 Long before claims to the region were made by Anglo-Americans, Spanish colonials and later Mexicans settled a series of communities along the south banks of the river, which provided protection from Comanche and Apache raids from the north.Prior to major water-control projects on the Rio Grande such as Elephant Butte Dike, which was constructed in the early 20th century, the river flooded often.San Elizario was a relatively large community south of the river from its founding in 1789 until an 1829 flood changed the course of the river, leaving San Elizario on "La Isla", a new island between the new and old channels of the Rio Grande.