Migrants can enter a country legally—with passport, visa, working permit, or other authorization—or illegally. Some aliens enter a country legally but on a temporary basis (as a student or tourist, for example), but then remain after their official departure date. Others arrive claiming the right of political asylum but actually seeking economic opportunity. The Department of Homeland Security estimates that between one-fourth and one-third of the illegal residents in the United States entered the country legally but then overstayed their visas.

Although it is impossible to determine the precise number of people residing illegally in the United States, a number that changes daily, most authorities estimate there are anywhere from 10 to 12 million. About 55% have come from Mexico, another 20% to 25% from other Latin American countries and the Caribbean, 13% from Asia, and the remainder from Canada, Europe, and Africa. The rising tide of emotion against unauthorized immigrants is directed mainly against those from Latin America, most of whom are unskilled workers.

Once they are in the United States, Latin American immigrants find work in agricultural fields, animal slaughtering and meat packing facilities, construction, hotels, and restaurants. Many work in private residences as maids, nannies, and gardeners. While most undocumented workers initially enter California, Arizona, Texas, or Florida, and many remain in those states, they go where they find jobs. Many blend into the large migrant communities not just of Los Angeles, El Paso, and Houston, for example, but also those of Chicago and New York City. Iowa and North Carolina have some of the fastest-growing populations of illegal immigrants. The demand for their labor is great enough that nearly all of the males have higher labor force participation rates than native-born men.

Concern over the growing number of illegal aliens has been reflected in a number of actions in recent years.

• Security fears since the September 11, 2001, assaults on the World Trade Center and Pentagon have led to more stringent visa applicant background checks, greater restrictions on admitting refugees and asylum seekers, stricter enforcement of Immigration and Naturalization Service (INS) rules on alien residency reports and visa time restrictions, and stricter border controls.

• Greater efforts are being made to deter illegal crossings along the 3380-kilometer (2100-mi) U.S.-Mexico border. To supplement the 120 kilometers (75 mi) of steel fences near a few U.S. cities, the Bush administration in 2007 proposed 1125 kilometers (700 mi) of new fencing, and Congress approved money for a small portion of it. The administration also increased the number of Border Patrol agents, who use automotive vehicles, helicopters, unmanned aircraft known as drones, night-vision cameras, and hidden electronic sensors for surveillance. In parts of Arizona and California, self-appointed Minutemen—groups of volunteer militia—patrol the border “to protect our country from a 40-year long invasion across our southern border with Mexico,” as one vigilante put it.

• Because the burden of coping with illegal immigration falls mostly on state and local governments, four states (Florida, Texas, Arizona, and California) have sued the federal government—so far unsuccessfully—to win reimbursement for the costs of illegal immigration. Similarly, the U.S.-Mexico Border Counties Coalition, composed of representatives from the 24 counties in the United States that abut Mexico, has not yet succeeded in getting the federal government to reimburse local administrations for money spent on legal and medical services for illegal aliens. These services include the detention, prosecution, and defense of immigrants; emergency medical care; ambulance service; and autopsies and burials for the hundreds who die each year while trying to cross the border.

• Concerned that large numbers of unauthorized immigrants impose a financial burden on taxpayers, congest schools and public health clinics, and result in the reduction of services to legal residents, voters in California approved Proposition 187, which barred illegal immigrants and their families from public schools, social services, and nonemergency health care. The measure also required state and local agencies to report suspected illegal immigrants to the Immigration and Naturalization Service and to certain state officials. The courts struck down Proposition 187, declaring most of the provisions to be unconstitutional, and the measure was never implemented.

• In Arizona, a law targeting employers of undocumented workers took effect on January 1, 2008. Employers are required to check the status of each worker with the federal government. A company found to have knowingly hired an illegal resident has its business license suspended for 10 days for the first offense. A second offense results in the permanent revocation of the business license. Other states are considering similar legislation.

Millions of illegal residents managed to legalize themselves by taking advantage of government amnesties offered between 1984 and 2000. In his State of the Union address in 2013, President Obama called for a temporary-worker program that would legalize the presence of millions of undocumented workers and lead toward citizenship. Congressional efforts to pass a comprehensive immigration reform bill failed in 2007, however. It called for greater border security, a guest worker program, and a path to citizenship for those already here.

Do you believe the federal government has an obligation to fully or partially reimburse state and local governments for the costs of education, medical care, incarceration, and other legal services for unauthorized immigrants? Why or why not?