Illegal immigration to the United States refers to the act of foreign nationals violating U.S. immigration policies and national laws by immigrating to the United States without proper consent from the United States government.

In USA, illegal immigration mainly refers to the presence of 12 million undocumented Mexican-American immigrants in the United States. Mexican workers, recruited by U.S. corporations since the 1830s, have historically been allowed by the government to cross the border to work indefinitely--initially on railroads, later on farms--without interference.

Lawmakers have recently made more of an effort to enforce immigration paperwork requirements, for the following reasons-

1.     Terrorism-related fears stemming from the September 11th attacks,

2.     The emergence of Spanish as a second national language, and

3.    Concerns among some voters that the United States is becoming less demographically white.

Efforts to crack down on immigration paperwork violations have made life more difficult for U.S. Latinos, three-quarters of whom are U.S. citizens or legal residents.
At the same time, however, the current state of law with respect to undocumented immigrants is not very satisfactory--both because of the security risk posed by a completely porous border, and because of the labor abuses that undocumented immigrants often encounter. Efforts have been made to extend citizenship to undocumented immigrants under certain conditions, but these efforts have so far been blocked by policymakers who favor large-scale deportation.