Now, however, as violence on the border continues to increase, a new kind of immigrant to the United States is appearing: people seeking asylum to escape the drug-fueled brutality in Mexico.
More than 6,000 people were killed in the violence last year, and more than 8,000 in the two years since President Felipe Calderon sent thousands of troops into the drug war zones.
"Some families living on the frontier are leaving, and the easiest way to live in the U.S. for them is by asking for the status of refugee," said Damaso Morales, a professor of international studies at the Universidad Nacional Autonoma de Mexico, the largest university in Latin America. "It's a way to get into the U.S. in a legal way."
Already, there have been two celebrated cases of asylum-seekers: a journalist who fled the northern state of Chihuahua after drug cartels threatened him, and the mayor of Ciudad Juarez, a major border city opposite El Paso, Texas, who pulled out when drug traffickers threatened his family. Though both succeeded in getting into the U.S., their tactic is still relatively untested in U.S. courts.
Ana Maria Salazar, a U.S. deputy assistant secretary of defense during the Clinton administration who's now a political commentator in Mexico City, said people were moving away from the country's crime-plagued border towns, if not yet to the U.S.
"Many people fearing for their lives in border towns are moving to big cities within Mexico," said Salazar, who has Mexican and American citizenship. "As descriptions of the violence continue to become public, there will definitely be talk about the refugee status" in the U.S., although she added the violence would have to be "very high."
The increase in violence, experts said, has replaced immigration as the major source of friction in U.S.-Mexican relations. In March, Mexicans ranging from Calderon to local editorial writers were outraged when a U.S. official suggested that the government had lost control of some parts of the country to the drug lords.
The incident wasn't smoothed over until Secretary of State Hillary Clinton and President Barack Obama visited Mexico and acknowledged the U.S. bore a share of responsibility for Mexico's drug wars, not only from the billions of dollars sent south to purchase undocumented drugs but also because of the high-powered weapons that are purchased legally in U.S. border towns and sold to Mexican gangs.
The fear created by this border violence, Morales said, is "a real problem, as Mexicans are coming in to the U.S. claiming asylum. These people would rather be in jail in the U.S. waiting to see if Uncle Sam grants them mercy than be in Mexico, where drug traffickers are killing family members."
Although the number of people entering the United States may increase if the violence continues to escalate, the number of Mexican citizens emigrating to the U.S. has dropped almost 25 percent within the past five months, according to the U.S. Embassy in Mexico City. Though it's hard to say why, the faltering U.S. economy most often is blamed.
"The economy here is really tied up in the economy of the U.S.," Morales said. "Things are very different and are changing in this economic crisis."
Francisco Gonzalez, an associate professor of Latin American studies at Johns Hopkins University's School of Advanced International Studies in Washington, said officials on both sides of the border now worried more about the drug wars than about immigration.
"The country has become very violent," Gonzalez said, "and it is very easy to see that things there could get even worse."
