Immigration , mainly from Latin America and Asia , swelled during the 1990s , laying the groundwork for great changes in the demographic makeup of the U.S. population in coming decades , such as Hispanics replacing African-Americans as the largest minority . Despite tougher border scrutiny after the September 11 attacks , nearly 8 million immigrants came to the United States from 2000 to 2005 — more than in any other five-year period in the nation 's history . Almost half entered illegally
September 11 attacks
September 11 attacks
History of the United States (1991–2008)