The international border between the United States and Mexico runs from San Diego, California, and Tijuana, Baja California, in the west to Matamoros, Tamaulipas, and Brownsville, Texas, in the east. It traverses a variety of terrains, ranging from major urban areas to inhospitable deserts. From the Gulf of Mexico it follows the course of the Rio Grande (Río Bravo del Norte) to the border crossing at El Paso, Texas, and Ciudad Juárez, Chihuahua; westward from that binational conurbation it crosses vast tracts of the Sonoran and Chihuahuan Deserts, the Colorado River Delta, and the northernmost tip of the Baja California Peninsula before reaching the Pacific Ocean.
The border’s total length is 1,951 miles (3,141 km), according to figures given by the International Boundary and Water Commission.[1] It is the most frequently crossed international border in the world, with some 350 million people crossing (legally) every year.[2]
Geography
The international border extends over 1,952 miles (3,141 km). The boundary follows the middle of the Rio Grande — according to the 1848 Treaty of Guadalupe Hidalgo between the two nations, “along the deepest channel” — from its mouth on the Gulf of Mexico a distance of 1,254 miles (2,019 km) to a point just upstream of El Paso, Texas, and Ciudad Juárez, Chihuahua. It then follows an alignment westward overland and marked by monuments a distance of 533 miles (858 km) to the Colorado River. Thence it follows the middle of that river northward a distance of 24 miles (38 km), and then it again follows an alignment westward overland and marked by monuments a distance of 141 miles (226 km) to the Pacific Ocean. The region along the boundary is characterized by deserts, rugged mountains, abundant sunshine and by two major rivers — the Colorado River and the Rio Grande (Río Bravo del Norte) — which provide life-giving waters to the largely arid but fertile lands along the rivers in both countries.
The U.S. states along the border, from west to east, are:
California, Arizona, New Mexico, and Texas.
The Mexican states are:
Baja California, Sonora, Chihuahua, Coahuila, Nuevo León, and Tamaulipas.
In the United States, Texas has the longest stretch of the border of any state, while California has the shortest. In Mexico, Chihuahua has the longest border, while Nuevo León has the shortest.
The total population of the borderlands — defined as those counties and municipios lining the border on either side — stands at over 20 million people.
History
With the exception of a small number of minor Rio Grande border disputes, since settled, the current course of the border was finalized by the 1848 Treaty of Guadalupe Hidalgo and the 1853 Gadsden Purchase. Whether the border between Mexico and the breakaway Republic of Texas followed the Rio Grande or the Nueces River further north was an issue never settled during the existence of that Republic, and the uncertainty was one of the direct causes of the 1846–48 Mexican-American War. An earlier agreement, signed during the Mexican War of Independence by the United States and Imperial Spain, was the 1819 Adams-Onís Treaty, which defined the border between the republic and the colonial empire following the Louisiana Purchase of 1804.
