The Mexico – United States barrier — also known in the United States as the border fence or border wall — is actually several separation barriers designed to prevent illegal movement across the Mexico – United States border. The barriers were built as part of three larger "Operations" to taper transportation of illegal drugs manufactured in Latin America and illegal immigration: Operation Gatekeeper in California, Operation Hold-the-Line  in Texas, and Operation Safeguard in Arizona. The barriers are strategically placed to mitigate the flow of illegal border crossings along the Mexico – United States international border into the Southwestern United States. Opponents claim the barriers are a taxpayer boondoggle, an ineffective deterrent and that the barriers inappropriately jeopardize the health and safety of those seeking illegal entry into the United States, as well as destroy animal habitat, prevent animals from reaching water, disturb animal migration patterns, and otherwise damage the environment.
The 1,951 mile (3,141 km) border between the United States and Mexico traverses a variety of terrains, including urban areas and deserts. The barrier is located on both urban and uninhabited sections of the border, areas where the most concentrated numbers of illegal crossings and drug trafficking have been observed in the past. These urban areas include San Diego, California and El Paso, Texas. As of August 29, 2008, the U.S. Department of Homeland Security had built 190 miles (310 km) of pedestrian border fence and 154.3 miles (248.3 km) of vehicle border fence, for a total of 344.3 miles (554.1 km) of fence. The completed fence is mainly in New Mexico, Arizona, and California, with construction under way in Texas. 
U.S. Customs and Border Protection reported that it had more than 580 miles (930 km) of fence in place by the second week of January, 2009. Work is still under way on fence segments in Texas and on the Border Infrastructure System in California.
The border fence is not one continuous structure and is actually a grouping of short physical walls that stop and start, secured in between with "virtual fence" which includes a system of sensors and cameras monitored by Border Patrol Agents. As a result of the success of the barrier, there has been a marked increase in the number of people trying to illegally cross the Sonoran Desert and crossing over the Baboquivari Mountain in Arizona. Such illegal immigrants must cross 50 miles (80 km) of inhospitable terrain to reach the first road, which is located in the Tohono O'odham Indian Reservation.
There have been around five thousand migrant deaths along the Mexico-U.S. border in the last thirteen years, according to a document created by the Human Rights National Commission of Mexico, also signed by the American Civil Liberties Union Between 43 and 61 people died trying to cross the Sonoran Desert during that same time period; 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 and 2004, 1,954 persons are officially reported to have died along the US-Mexico border. Since 2004, the bodies of 1086 migrants have been recovered in the southern Arizona desert.
U.S. Border Patrol Tucson Sector reported on Oct. 15, 2008 that its agents were able to save 443 illegal aliens from certain death after being abandoned by their smugglers, during FY 2008, while reducing the number of deaths by 17 percent from 202 in FY 2007 to 167 in FY 2008 . Without the efforts of these agents, hundreds more could have died in the unforgiving deserts of Arizona.
The sustained trend of quality enhancements including additional manpower, growing infrastructure and improved technology have allowed the Tucson Sector agents to expand border security, reducing the number of apprehensions at the borders by 16 percent compared with fiscal year 2007. Tucson Sector agents apprehended 317,696 illegal aliens that attempted to circumvent enforcement efforts at the border and interior checkpoints. 12,267 of those arrested were from countries other than Mexico.
U.S. Representative Duncan Hunter, a Republican from California and the then-chairman of the House Armed Services Committee, proposed a plan to the House on November 3, 2005 calling for the construction of a reinforced fence along the entire United States – Mexican border. This would also include a 100-yard (91 m) border zone on the U.S. side. On December 15, 2005, Congressman Hunter's amendment to the Border Protection, Anti-terrorism, and Illegal Immigration Control Act of 2005 (H.R. 4437) passed in the House. This plan calls for mandatory fencing along 698 miles (1,123 km) of the Mexican border. On May 17, 2006 the U.S. Senate proposed with Comprehensive Immigration Reform Act of 2006 (S. 2611) what could be 370 miles (600 km) of triple layered-fencing and a vehicle fence. Although that bill died in committee, eventually the Secure Fence Act of 2006 was passed by Congress and signed by President Bush on October 26, 2006.
The government of Mexico, as well as intellectuals of that country and ministers of several Latin American countries have condemned the plans. Rick Perry, governor of Texas, also expressed his opposition saying that instead of closing the border it should be opened more and through technology support legal and safe migration. The barrier expansion has also been opposed by a unanimous vote of the Laredo, Texas City Council. Laredo's Mayor, Raul G. Salinas, is concerned about defending his town's people by saying that the Bill which includes miles of border wall would devastate Laredo. He states "these are people that are sustaining our economy by forty percent, and I am gonna [sic] close the door on them and put [up] a wall? You don't do that. It's like a slap in the face." He hopes that Congress would revise the Bill that better reflects the realities of life on the border. There are no plans to build border fence in Laredo at this time.
On September 29, 2006, by a vote of 80–19 the U.S. Senate confirmed H.R. 6061 authorizing, and partially funding the "possible" construction of 700 miles (1,125 km) of physical fence/barriers along the border. The very broad support implies that many assurances have been made by the Administration, to the Democrats, Mexico, and the pro "Comprehensive immigration reform" minority within the GOP, that Homeland Security will proceed very cautiously. Michael Chertoff, announced that an eight-month test of the virtual fence, he favors, will precede any construction of a physical barrier. Any large scale fence construction will occur late in the Bush presidency, if at all, prior to a new administration.
On October 26, 2006, President George W. Bush signed H.R. 6061 which was voted upon and passed by the 109th Congress of the United States. The signing of the bill comes right after a CNN poll shows us that most Americans "prefer the idea of more Border Patrol agents to a 700-mile (1,125-kilometer) fence." There is a down payment of $1.2 billion to the Department of Homeland Security marked for border security, but not specifically for the border fence.
As of January 2010 the fence project has been completed from san diego,ca all the way to yuma,arizona from there it continues to texas and consist of a fence 21ft tall 6ft deep in the ground,concreted in a trench 3ft wide.it is also filled with 5000psi concrete,there were no fatality's during construction but there were 4 serious injuries with multiple aggressions against building crews,there was one report shooting with no injury to a crew member in Mexicali region.All fence sections are south of the all American canal and have access roads giving border guards the resources to get to any point quick and easy.including the dunes area where a border agent was killed 3 years ago and is now sealed off.
House Majority Leader Steny H. Hoyer (D-MD) announced in January 2007 that Congress will revisit the fence plan, while committee chairs are holding up funding until a comprehensive border security plan is presented by the Department of Homeland Security. Both Senators from Texas, John Cornyn (R-TX) and Kay Bailey Hutchison (R-TX), advocate revising the plan.
Construction of the border fence will not be subject to any laws. This is because in 2005 the Real ID Act, attached as a rider to a supplemental appropriations bill funding the wars in Iraq and Afghanistan, decreed, “Not withstanding any other provision of law, the Secretary of Homeland Security shall have the authority to waive all legal requirements such Secretary, in such Secretary’s sole discretion, determines necessary to ensure expeditious construction of the barriers and roads. On September 22, 2005, Secretary of Homeland Security Michael Chertoff used his new power to “waive in their entirety” the Endangered Species Act, the Migratory Bird Treaty Act, the National Environmental Policy Act, the Coastal Zone Management Act, the Clean Water Act, the Clean Air Act, and the National Historic Preservation Act to extend triple fencing through the Tijuana River National Estuarine Research Reserve near San Diego. The Real ID Act further stipulates that his decisions are not subject to judicial review, and in December 2005 a federal judge dismissed legal challenges by the Sierra Club, the Audubon Society, and others to Chertoff’s decision.
Secretary Chertoff exercise his waiver authority on April 1, 2008. In June, 2008 the U.S. Supreme Court declined to hear the appeal of a lower court ruling upholding the waiver authority in a case filed by the Sierra Club. (Associated Press) In September, 2008 a federal district court judge in El Paso dismissed a similar lawsuit brought by El Paso County, Texas.( Associated Press)
By January, 2009, U.S. Customs and Border Protection and the U.S. Department of Homeland Security had spent $40 million on environmental analysis and mitigation measures aimed at blunting any possible adverse impact that the fence might have on the environment. On January 16, 2009 DHS announced it was pledging an additional $50 million for that purpose, and signed an agreement with the U.S. Department of the Interior for utilization of the additional funding.
In the spring of 2007 more than 25 landowners, including a corporation and a school district, from Hidalgo and Starr County in Texas refused border fence surveys, which would determine what land was eligible for building on, as an act of protest.
In July, 2008, Hidalgo County and Hidalgo County Drainage District No. 1 entered into an agreement with the U.S. Department of Homeland Security for the construction of a project that combines the border fence with a levee to control flooding along the Rio Grande. Construction of two of the Hidalgo County fence segments are under way; five more segments are scheduled to be built during the fall of 2008; the Hidalgo County section of the border fence will constitute 22 miles (35 km) of combined fence and levee.
Eloisa Garcia Tamez, a Lipan Apache of Encantada-Ranchito El Calaboz, Texas rancheria, challenged the United States Department of Homeland Security, the U.S. Customs and Border Patrol and the Army Corps of Engineers in a constitutional law case, Eloisa G. Tamez v. Michael Chertoff/U.S. Department Homeland Security. Civil Action #1:08-CV-044.
In August, 2008, UT-Brownsville reached an agreement with the U.S. Department of Homeland Security for the university to construct a portion of the fence across and adjacent to its property. The final agreement, which was filed in federal court on Aug. 5 and formally signed by the Texas Southmost College Board of Trustees later that day, ended all court proceedings between UTB/TSC and DHS. On August 20, 2008, the university sent out a request for bids for the construction of a 10-foot (3.0 m) high barrier that incorporates technology security for its segment of the border fence project. The southern perimeter of the UTB/TSC campus will be part of a laboratory for testing new security technology and infrastructure combinations. The border fence segment on the UTB campus was substantially complete by December, 2008.
There have been campus protests against the wall by students who feel it will harm their school. Mexico has urged the US to alter its plans for expanded fences along their shared border, saying they would damage the environment and harm wildlife.
In June 2007 it was announced that a section of the barrier had been mistakenly built from 1 to 6 feet (1.8 m) inside Mexican territory. This will necessitate the section being moved at an estimated cost of over 3 million dollars.
In September 2007 a U.S. Fish and Wildlife Service spokesperson announced that 60-75 percent of the protected lands and refuges in the Rio Grande Valley of Texas would be affected by the border wall. Several environmental groups claimed it would be a major detriment, as it would block river access and destroy essential vegetation for many native and migratory species.
On January 27, 2008 a U.S. Native American human rights delegation, which included Margo Tamez, (Lipan Apache-Jumano Apache) and Teresa Leal (Opata-Mayo) reported the removal of the official International Boundary obelisks of 1848 by the U.S. Department of Homeland Security in the Las Mariposas, Sonora-Arizona sector of the Mexico-U.S. border. The obelisks were moved southward approximately 20 meters, onto the property of private land-owners in Sonora, as part of the larger project of installing the 18-foot (5.5 m) steel barrier wall.
In April 2008 the Department of Homeland security announced plans to waive more than 30 environmental and cultural laws to speed construction of the barrier. Despite claims from then Homeland Security Chief Michael Chertoff that the department would minimize the construction's impact on the environment, critics in Arizona and Texas asserted the fence endangered species and fragile ecosystems along the Rio Grande. Environmentalists expressed concern about butterfly migration corridors and the future of two species of local wildcats, the ocelot and the jaguarundi.
After the fence was erected in Arizona, the Borderlands Jaguar Detection Project and Big Cat Rescue blogspot reported in December, 2008 that "Macho B (a male jaguar long observed) has been seen again in Arizona!" and that the animal had been photographed again on U.S soil. The groups had feared that the border wall would ruin "the big guy's chances in the US, but I'm happy to say I was wrong," the blogspot reported.
U.S. Customs and Border Protection (CBP) conducted environmental reviews of each pedestrian and vehicle fence segment covered by the waiver, and published the results of this analysis in Environmental Stewardship Plans (ESPs). Although not required by the waiver, CBP has conducted the same level of environmental analysis (in the ESPs) that would have been performed before the waiver (in the “normal” NEPA process) to evaluate potential impacts to sensitive resources in the areas where fence is being constructed.
CBP coordinates with federal and state resource agencies, tribes and other stakeholders as fence construction plans continue to develop, and continues to seek input—and make appropriate changes—to address stakeholder concerns. CBP is ensuring that the ESPs are implemented by incorporating these plans into its construction contracts. Contractors have been required to implement the Best Management Practices outlined in the ESPs to protect resources that are part of these plans. In addition, CBP has hired third-party, independent biological resource monitors to advise the U.S. Corps of Engineers construction managers and construction contractors, and to document performance in meeting these plans. CBP is providing construction contractors with training, before construction begins, on sensitive natural resources in the project area, and has outlined procedures that are to be followed if an endangered species is encountered during construction.
CBP also addressed the identification and preservation of cultural resources in the areas of fence construction in a similar fashion, maintaining continuous consultation with State Historic Preservation Offices (SHPS) and Native American Tribal Historic offices regarding cultural resources and potentially sensitive sites that could be affected. CBP developed agreements with the SHPS and the U.S. Bureau of Land Management for additional study and data recovery at sites of cultural significance. CBP has funded more than 50 excavations and recovered hundreds of artifacts that otherwise might never have been uncovered.
CBP has hired third-party, independent cultural resource monitors, including trained archeologists, to advise Corps of Engineers construction managers and construction contractors, and to document any pertinent discoveries. These specialists have performed surveys of corridors, access roads and staging areas to develop a comprehensive list of significant sites linked to the fence project, and have identified more than 100 previously unknown sites.
By August, 2008, more than 90 percent of the southern border in Arizona and New Mexico had been surveyed. The remaining portions will be surveyed in the next three months. In addition, 80 percent of the California/Mexico border has been surveyed.
Generally, Hispanic and Asian communities favor more open borders and legalization, while Whites and Blacks favor enforcement and closed borders; When queried to rate most to least important issues, 2008 polls revealed that only 10% rate immigration as their "top issue," whereas (40%) rate the economy as most important, (20%) rate the Iraq War as most important, and (20%) rate healthcare as most important.
A May 1, 2008 Rasmussen Reports poll revealed that Texans favored building a fence along the U.S. border with Mexico, with 52 percent in favor and 37 percent against (margin of error: +/- 4.5 percentage points). An August 18, 2007 nationwide poll asking the same question, found 56 percent in favor and 31 percent against. This poll also found that among those who identified themselves as Republicans 75 percent supported building a fence along the border.