A decade that left a mark on U.S. history

The decade began with a national sigh of relief — no Y2K terrorist attack or computer meltdown. A traveler named Luis Salcedo, boarding a flight in New Orleans on Jan. 1, 2000, summed it up: "Nothing to worry about now."

Not with the lowest unemployment rate in nearly 30 years and a stock market that had just closed at a historic high. Not in the world's only superpower.

So began a decade when America experienced its worst attack by foreigners and its worst natural disaster; its second-deadliest domestic plane crash, and the most divisive, protracted presidential election since 1876.

There were two wars, both longer than World War II; two stock market crashes; and two recessions, including the worst since the Great Depression.

The first African-American president was inaugurated in a city where, 60 years earlier, Barack Obama's father couldn't have sat at the same lunch counter as a white man.

Americans learned that there was water on the moon and that Tiger Woods wasn't perfect.

Wikipedia, Twitter, YouTube, MySpace, Facebook, Skype and Hulu all debuted, as did the iPod, the iPhone and iTunes. Books were joined by e-books. Television broadcasting moved from analog to digital, and TV viewing from cathode ray tubes to flat screens.