Immigration to the United States becomes illegal when a person settles without prior authorization by the U.S. government, or by breaking the terms of entry. This act of remaining for an indefinite period is a violation of U.S. immigration laws.
Fast facts on illegal immigration:
Governing American immigration law is the Immigration and Nationality Act.
Census data and other sources show that the illegal population is somewhere between 7 million and 20 million.
Between 400,000 and 700,000 illegal immigrants enter the United States each year.
The U.S. Customs and Border Protection is the agency tasked with detaining those attempting to enter the United States illegally.
When polled, 58% of Mexicans say, "The territory of the United States' southwest rightfully belongs to Mexico."