On September 11, 2001, members of an Islamic terrorist network called A1 Qaeda hijacked four commercial airliners. One crashed in rural Pennsylvania, one was flown into the Pentagon, and two were flown into the twin towers of New York City's World Trade Center. The towers burned and collapsed, killing some 3,000 persons, including many emergency workers. In response to these actions, the United States launched a war against terrorism. It attacked A1 Qaeda fighters in Afghanistan and sought their leader, Osama bin Laden. In addition, the United States attacked and defeated Afghanistan's ruling power, the Taliban, which had supported Al Qaeda.
In October, 2001, it was discovered that envelopes containing spores of anthrax—an often fatal bacterial disease—were being sent through the mail. Of the thousands of persons potentially exposed to the spores, more than a dozen were infected and five died.
These events disrupted an already weakened United States economy. In decline by the beginning of 2001, the economy suffered its worst year since the early 1990's. In 2003 Congress passed major tax-cut legislation. See also bibliographies following articles on each state, on major American wars, and on the beginning of 2001, the economy suffered its orst year since the early 1990's. In 2003 Congress passed major tax-cut legislation with the support of the Bush administartion.
As part of nationwide efforts to prepare for and prevent possible terrorist attacks, the Department of Homeland Security was established. In 2003 President Bush, warning that the government of Saddam Hussein in Iraq had developed weapons of mass destruction that posed a serious and immediate threat, ordered American armed forces to invade Iraq. Together with armed forces from Great Britain and a few other countries, they toppled the Hussein government from power in a six-week war known as Gulf War II. No weapons of mass destruction were found, however, and U.S. troops remained in Iraq fighting insurgents. In 2004 President Bush won reelection. That same year, Bush formed a commission to investigate how he had received inaccurate information about Iraq's weapons of mass destruction. In 2005, the commission reported that federal intelligence agencies had inadequately gathered data concerning the weapons.
Hurricane Katrina struck the Gulf Coast in 2005. The hurricane was one of the worst natural disasters in the history of the United States. The hurricane damaged coastal areas from Louisiana to Florida, and more than 1,800 people died as a result. Parts of New Orleans system of levees failed. Most of the city was submerged for weeks.In several U.S. cities, millions of people protested a proposed 2006 law that would increase penalties for illegal immigrants. Around 12 million immigrants, mainly from Central America, live in the United States illegally, according to experts. Later in 2006, Bush authorized new fences to be constructed along the border of the United States and Mexico.