How many states border Mexico?

Four U.S. states share a border with Mexico: California, Arizona, New Mexico, and Texas, listed here from west to east. The U.S.-Mexico border runs about 1,954 miles total from the Pacific Ocean at Imperial Beach south of San Diego in California to the Gulf of Mexico at the mouth of the Rio Grande east of Brownsville, Texas.

California's border with Mexico measures about 140 miles, all surveyed line, ending at the Pacific. The border crosses the urban San Diego-Tijuana metropolitan region, the Imperial Valley agricultural area, and ends at the All American Canal and the Colorado River near Yuma. Arizona's border with Mexico measures about 372 miles, all surveyed line from Yuma east to the New Mexico border. The terrain crosses the Sonoran Desert, the Tohono O'odham Nation reservation, and the U.S.-Mexico border crossings at Nogales, Douglas, and Naco.

New Mexico's border with Mexico measures about 180 miles, all surveyed line from the Arizona border east to El Paso, Texas. The terrain crosses the Chihuahuan Desert. The border crossings include Columbus and Antelope Wells. Texas has by far the longest border with Mexico at about 1,254 miles, almost entirely along the Rio Grande from El Paso south and east to the Gulf of Mexico.

The Rio Grande was established as the boundary by the Treaty of Guadalupe Hidalgo of February 2, 1848 ending the Mexican-American War. Major U.S.-Mexico border crossings along the Rio Grande include El Paso/Ciudad Juarez (the largest international metropolitan area on the border), Eagle Pass/Piedras Negras, Laredo/Nuevo Laredo (the busiest land port for trade in the United States), McAllen-Hidalgo/Reynosa, and Brownsville/Matamoros. Border issues are a continuing major theme in American politics including immigration enforcement, drug trafficking, trade, and water rights along the Rio Grande and Colorado Rivers.

The border originated through the Treaty of Guadalupe Hidalgo of February 2, 1848 and the Gadsden Purchase of December 30, 1853, which together transferred about 555,000 square miles from Mexico to the United States. The border has been surveyed and refined by various treaty commissions, including the International Boundary Commission established 1889 (now the International Boundary and Water Commission since 1944). Border infrastructure includes about 700 miles of physical fencing or wall constructed in various phases since the 1990s. The U.S. Border Patrol, established 1924, is responsible for patrolling between official ports of entry. Each year about 350 million border crossings occur at official ports, supporting about 750 billion dollars in annual U.S.-Mexico trade.