2001

• Sept. 11: Terrorists hijack four jetliners and crash them into the World Trade Center, the Pentagon and a Pennsylvania field. The twin towers and Seven World Trade Center collapse.

• Sept. 13: Osama bin Laden identified as prime suspect in the attack.

• Sept. 14: Nineteen hijackers identified and linked directly to bin Laden.

• Sept. 17: Wall Street trading resumes, ending stock market's longest shutdown since the Great Depression. Dow loses 684.81 points, its worst-ever one-day point drop.

• Oct. 7: First airstrikes launched in Afghanistan. Bin Laden, in videotaped message, praises God for Sept. 11 attacks.

• Oct. 26: President Bush signs anti-terrorism bill giving police unprecedented ability to search, seize, detain and eavesdrop in pursuit of possible terrorists.

• Nov. 25: First wave of Marines lands near Taliban stronghold of Kandahar.

• Dec. 22: Hamid Karzai and his transitional government sworn in to lead Afghanistan.

2002

• Feb. 14: Leaders of House and Senate intelligence committees announce joint inquiry of intelligence community's failure to prevent the attacks.

• Sept. 18: Investigator for joint inquiry testifies that intelligence agencies disregarded many warnings that terrorists might use planes as bombs.

• Nov. 25: Bush signs legislation creating Department of Homeland Security.

• Nov. 27: Bush signs bill establishing independent commission to investigate the Sept. 11 attacks.

• Dec. 11: Congressional inquiry issues final report on intelligence failures leading up to terrorist attacks. Key recommendations include creating Cabinet-level director of national intelligence.

• Dec. 13: WTC death toll drops to 2,792, one of several drops since the first anniversary of the attacks.

2003

• Jan. 1: Thousands of newly hired government workers begin screening every checked bag at the nation's commercial airports for explosives.

• Jan. 27: The independent 9/11 commission, headed by ex-New Jersey Gov. Thomas H. Kean, launches its 16-month investigation.