The United States Mexico barrier is actually several separation barriers designed to prevent illegal immigration into the United States from the territory of adjacent Mexico. Its chief target is Mexican nationals and other Latin Americans, although in recent years other groups (particularly Asians of different nationalities) have also been using the porous Mexican border to secure access to the USA (the Border Patrol refers to those from other countries as "Other Than Mexican" (OTM)). The barriers were built as part of three larger "Operations" to control illegal immigration, Operation Gatekeeper in California, Operation Hold-the-Line in Texas, and Operation Safeguard in Arizona. The intention of these barriers is to force immigrants to cross the border through more difficult lands, with the assumption that this will deter migration. Some United States/Mexico border scholars have claimed that these operations are just a public relations ploy used to convince U.S. citizens that the border is "secure", while the economy benefits from the continuing flow of cheap labor across the border.

The 3140 km (1,951 mile) border between the United States and Mexico traverses a variety of terrains, including urban areas and deserts. The barrier is located in the urban sections of the border, the areas that have been the location of the greatest number of illegal crossings in the past. These urban areas include San Diego, California, and El Paso, Texas. As a result of the success of the barrier, there has been a marked increase in the number of people trying to cross the Sonoran Desert and the Baboquivari Mountains in Arizona. Such migrants must cross 80 km (50 miles) of inhospitable terrain to reach the first road, which is located in the Tohono O'odham Indian Reservation.

Between October 1, 2003, and April 30, 2004, 660,390 people were detained by the United States Border Patrol as they tried to cross the border illegally. Between 43 and 61 people have died trying to cross the Sonoran Desert during that same time period, a value three times that of the same period the previous year. In October, 2004 the Border Patrol announced that 325 people had died crossing the entire border during the previous 12 months. Between 1998-2004, 1,954 persons are officially reported to have died along the US/Mexico border.

See also

• Immigration
• Immigration to the United States
• List of United States Immigration Acts
• Immigrant deaths along the U.S.-Mexico border