In 1990, law enforcement agents discovered the first illicit cross-border tunnel, in Douglas, Ariz. Since then, the U.S. Border Patrol and Drug Enforcement Administration have uncovered at least 106 more subterranean pathways crossing the border between Mexico and the states of Arizona and California. The U.S. Border Patrol says these tunnels are rudimentary, designed to achieve the goals of the drug cartels and human traffickers who use them to smuggle drugs and people.
As cross-border traffic becomes more lucrative, so does the engineering and construction of the tunnels. The U.S. Border Patrol plugs discovered tunnels quickly, but new routes appear seemingly overnight.