The river known as the boundary between Texas and Mexico is the Rio Grande. This significant river flows approximately 3,051 kilometers (1,885 miles) from the San Juan Mountains in Colorado to the Gulf of Mexico. The Rio Grande serves as both a natural and political boundary between the two countries, and it plays a crucial role in regional ecology and economy. It supports various ecosystems and is essential for agriculture, recreation, and water supply in the areas it traverses. The river has historical significance, too, being important to local cultures for centuries.