A section of the controversial US-Mexico border fence expansion project crosses previously pristine desert sands at sunrise on March 14, 2009, between Yuma, Arizona and Calexico, California. The barrier stands 15 feet tall and sits on top of the sand so it can lifted by a machine and repositioned whenever the migrating desert dunes begin to bury it. The almost seven miles of floating fence cost about $6 million per mile to build. #

A deported migrant climbs the US-Mexico border fence as he prepares for the 6th annual Marcha Migrante, or Migrant March, in Tijuana, on February 2, 2011. The Tijuana to Mexicali pilgrimage was organized by the group Border Angels to raise awareness on immigration issues. #

U.S. Border Patrol agent Manny Villalobos (center) patrols with other agents along the international border between Mexico and the United States near San Diego, California, on March 26, 2013. #

Soldiers prepare to enter a tunnel during a presentation to the media in Tijuana, on November 16, 2011. Police discovered a "major cross-border drug tunnel" running to California from Mexico, and seized 14 tons of marijuana, authorities said. The tunnel linked warehouses in an industrial park south of San Diego and the Mexican border city of Tijuana. #

Electrical breakers inside a cross-border tunnel located underneath a water purifying plant in Tecate, on December 6, 2012. The tunnel, which was still under construction, was found due to an anonymous tip. It has no exit to the U.S. but a ventilation system, electricity and a water pump. Seven people who were found working on the tunnel when it was discovered were arrested by the authorities, reported local media. #

Immigrants hide from a border patrol vehicle while waiting for a chance to cross into the United States at the border fence on the outskirts of the Tijuana, on September 19, 2009. #

A Predator drone operated by U.S. Office of Air and Marine (OAM), taxis towards the tarmac for a surveillance flight near the Mexican border, on March 7, 2013 from Fort Huachuca in Sierra Vista, Arizona. The OAM, which is part of U.S. Customs and Border Protection, flies the unmanned - and unarmed - MQ-9 Predator B aircraft an average of 12 hours per day at around 19,000 feet. The drones, piloted from the ground, search for drug smugglers and immigrants crossing illegally from Mexico into the United States. #

Clouds of dust kicked up by border patrol vehicles hang in the air along the US-Mexico border fence as agents carry out special operations on July 30, 2009 near the rural town of Campo, some 60 miles east of San Diego. #

Mauricia Horta Fuentes, 36, stands for a portrait along the fence marking the US-Mexico border in Tijuana, Mexico, on June 23, 2012. Fuentes, who lived and worked in the United States for years, drove up to a roadblock in Escondido, California, in September, 2008, on her way to pick up kids from school. Since then she has been cut off from her children, and has been forced to create a new life in her old country. #

In this image released by the Mexicali Public Safety Department, a man holds up an improvised cannon that was confiscated earlier in the day, February 26, 2013. Police in the border city say the cannon was used to hurl packets of marijuana across a border fence into California. #

Monument 245, viewed from the Mexico side of the border, in Tecate, by a Google Street View van. There are 276 such monuments lining the border, almost all built in the 1890s. #

An undocumented immigrant is detained by the U.S. Border Patrol near the US-Mexico border on April 11, 2013 near Mission, Texas. A group of 16 immigrants from Mexico and El Salvador said they crossed the Rio Grande River from Mexico into Texas during the morning hours before they were caught. The Rio Grande Valley sector of has seen more than a 50 percent increase in illegal immigrant crossings from last year, according to the Border Patrol. #

U.S. Border Patrol ranch liaison John "Cody" Jackson (right) rides with cattle rancher Dan Bell on Bell's ZZ Cattle Ranch at the US-Mexico border, on March 8, 2013 in Nogales, Arizona. Jackson meets regularly with local ranchers to coordinate the agency's efforts on border issues, including drug smuggling and illegal immigration from Mexico. Bell, a third generation rancher, grazes cattle on nearly ten miles of border property. #

In this photo provided by the U.S. Customs and Border Protection, a silver Jeep Cherokee that suspected smugglers were attempting to drive over the U.S.-Mexico border fence is stuck at the top of a makeshift ramp, on October 31, 2012 near Yuma, Arizona. U.S. Border Patrol agents from the Yuma Station seized both the ramps and the vehicle, which stalled at the top of the ramp after it became high centered. The fence is approximately 14 feet high where the would-be smugglers attempted to drive across the border. The two suspects fled into Mexico when the agents arrived at the scene. #

Property owner Bill Odle carries a gun and pocket knife as he discusses his perspective on Border Patrol near his home adjacent to the Arizona-Mexico border near Naco, Arizona, on March 29, 2013. Despite additional fencing and agents, Odle says their Border Patrol's presence on the line is only intermittent. #

Residents of Naco, Arizona join residents of Naco, Mexico for a volleyball match during the fourth "Fiesta Bi-Nacional" at the fence that separates the U.S. (left) and Mexico (right), on April 14, 2007. #

In numerous places, fences and roads marking the US-Mexico border simply end, only to start again miles away. This aerial view of such a road ends on a hillside on the border in southeast Arizona. #

Flor Gonzales, 19, from Chiapas, Mexico spends a night at the San Juan Bosco shelter for undocumented immigrants on March 9, 2013 in Nogales, Mexico. She said she was caught by the U.S. Border Patrol while trying for the first time to cross with a group into Arizona and was deported. The Juan Bosco shelter, located in Nogales, Mexico close to the U.S. border, allows immigrants to stay for up to three nights, either after they have been deported from the U.S. or before they attempt to cross the border into Arizona. #

U.S. border cops in western Arizona seized this off-road go-kart and trailer packed with marijuana, in an attempt by Mexican smugglers to beat beefed up border security. The Border Patrol's Yuma sector said agents and officers from the Cocopah Tribal Police Department spotted the single-seater go-kart hauling a trailer through the desert near Yuma, Arizona, and gave chase. The driver abandoned the homemade vehicle, which was spray painted a desert beige, fitted with knobbly off-road tires, and towing a trailer packed with 217 pounds of marijuana, about 100 yards from the border, and fled back to Mexico. #

David Walker, a Southern Arizona rancher, stands at the border wall with Mexico on August 15, 2010 in Hereford, Arizona, Walker was attending the United Border Coalition Tea Party Rally in support of Arizona's immigration law, SB1070 with conservative tea party activists along a remote stretch of the Arizona-Mexico border about 70 miles (113 km) west of Nogales. #

The United States/Mexico border fence, in Nogales, Arizona, on November 10, 2010. A town of about 20,000 people, it lies just north of the city of Nogales, Mexico, which has a population estimated at nearly ten times that number. #

In Union Hidalgo, southern Mexico, migrants ride on top of a northbound train, heading toward the US-Mexico border, on April 29, 2013. Migrants crossing Mexico to get to the U.S. have increasingly become targets of criminal gangs who kidnap them to obtain ransom money. #

Suspected drug smugglers flee across the Rio Grande River into Mexico on April 11, 2013 in Mission, Texas. Their marijuana smuggling atttempt was broken up by U.S. Border Patrol agents with helicopter support from the Office of Air and Marine. #

A woman, who declined to give her name, is hugged by her husband as they chat between the border fence separating Nogales, Arizona, and Nogales, Mexico, on July 28, 2010. #

A U.S. Border Patrol agent searches in dense brush for undocumented immigrants who had crossed from Mexico into the United States on April 11, 2013 in Penitas, Texas. In the last month the Border Patrol's Rio Grande Valley sector has seen a spike in the number of immigrants crossing the river from Mexico into Texas. With more apprehensions, they have struggled to deal with overcrowding while undocumented immigrants are processed for deportation. #

A pickup load of marijuana sits after being seized near the US-Mexico Border on April 11, 2013 in Mission, Texas. U.S. Border Patrol agents broke up a marijuana smuggling shipment from Mexico into Texas. #

A U.S. border patrol vehicle, seen from the Mexican side of the border in a long-exposure photograph, while driving near Otay Mountain on the outskirts of San Diego, California, on July 1, 2010. #