The major river known for forming the natural border between the United States and Mexico is the Rio Grande. This river flows for approximately 3,051 kilometers (1,885 miles) and serves as an essential water source for both countries. The Rio Grande is significant for its ecological diversity and serves as a critical transportation route for trade. It has cultural importance as well, reflecting the histories and traditions of communities on either side of the border. The river plays a vital role in regional hydrology and environmental conservation.