The border between the United States and Mexico stretches approximately 2,000 miles (3,220 kilometers) from the southern border of Texas to California. The La Paz Agreement (1983) defines the United States-Mexico border region as the area extending 100 kilometers (62 miles) on either side of the border. The border region includes 10 U.S. and Mexican states in total: Texas, New Mexico, Arizona and California in the U.S.; and Baja California, Sonora, Chihuahua, Coahuila, Nuevo Leon and Tamaulipas in Mexico.
According to data from the U.S. Census Bureau, the population of this area was about 13 million in 2000, and was expected to have doubled by 2005. The region boasts great ethnic and cultural diversity, with 154 Native American tribes living in the four U.S. border states. The border between the United States and Mexico is one of the busiest in the world, with 1 million border crossings being recorded every day in 2009. Truck traffic was also high, as trade between the countries was booming. Mexico's exports to the United States for 2009 were worth $185 billion, while the imports from the United States were worth $112 billion.
But actually determing where the border lay between the two countries was a matter of some dispute, and warfare, over a period of 200 years. In the early 19th century, the rapidly expanding United States claimed that Texas was part of the territory of Louisiana, and therefore had been rightfully acquired as part of the Louisiana Purchase from France (1803). The Spanish Empire, which then owned Mexico, claimed Texas as part of its territory, a dispute not resolved until the Adams-Onis Treaty in 1819, when the U.S. dropped its claim to Texas by instead purchased Florida from Spain.
Mexico broke away from Spain in 1821. Texas returned as a point of conflict between the two new nations. Americans and other non-Mexicans began to settle in eastern Texas in large numbers. These "Texians," often rejected Mexican rule, leading to the Texas Revolution of 1835. In 1845 the United States annexed Texas, prompting the U.S.-Mexico War (1846-48), which resulted in Mexico being forced to sell California and New Mexico to the U.S. The Treaty of Guadalupe Hidalgo (1848) failed to provide resolution to the dispute. Errors in surveying turned the Mesilla Valley into another disputed territory, which was finally sold to the United States as a part of the Gadsden Purchase (1853).
Territorial disputes were also related to changes in the course of the river Rio Grande (or Rio Bravo as it is called in Mexico). An area called El Chamizal was annexed by the U.S. in 1864, but the dispute continued for 99 years. In 1970, when the nations signed a treaty to resolve existing and future boundary disagreements. With territorial frictions eased, the countries were better able to pursue trade and other agreements.
Other problems also became evident, however, including the rapidly growing population as the result of the industrialization of Mexico and migrant workers seeking employment in the U.S. American businessmen tapped the potential of cheap Mexican labour force and established facilities and outlets in the border region. Over-population has brought with it issues of water supply, poor sanitation and poor medical services. In November 1993, the Border Environment Cooperation Commission (BECC) was established to develop environmental infrastructure projects, including wastewater treatment plants and drinking water systems.
In 1994 the United States and Mexico joined the North American Free Trade Agreement (NAFTA). Chief U.S. exports to Mexico are electronic equipment, motor vehicle parts, and chemicals. Mexico's imports from the United States stood at $112 billion (or 48 percent of total) in 2009. In the same year, exports from Mexico to the United States amounted to $185 billion (or 80 percent of the country's total exports).
Regardless of the tough controls implemented on the U.S.-Mexico border, illegal immigration persists as it is supported by criminal syndicates in Mexico. Smuggling of illegal goods and narcotics is also a problem. At the August 2007 North American Leaders' Summit in Montebello, presidents George W. Bush (b 1946) and Felipe Calderon (b 1962) announced the Merida Initiative. It envisages co-operation between North American and Central American countries to combat drug trafficking and organized crime.