After the World Trade Center towers fell, American patriotism -- especially as symbolized by the country's flag -- soared.
"People just felt the need to express a sense of national solidarity and a sense of national identification," said Columbia University history professor Eric Foner. "The most common way of doing that, as you know, was displaying the American flag."
Flags appeared faster than the chills Americans got when they realized they were under attack on their own soil -- the first such attack by foreign forces since Dec. 7, 1941, the day Japanese fighter-bombers attacked Pearl Harbor.
"Of course there was a great rallying after Pearl Harbor, but I don't think you had quite the kind of visible displays," Foner said.
After Sept. 11, it was all about displaying the Stars and Stripes. Every day became Flag Day as many Americans, struggling to contribute to the nation's cause, did so in the only way they knew how.
By the thousands, they stood single file, like soldiers going to war, but armed with banners instead of bayonets.
Stores quickly saw their stock of red, white and blue trinkets and flags depleted as flag makers worked overtime. It was something of a patriotic pandemonium.
One of the most memorable flags was one that flew at Ground Zero. In a scene reminiscent of U.S. soldiers raising the Stars and Stripes at Iwo Jima, firefighters unfurled a flag at the World Trade Center.
That image, captured on film, is now replicated at a wax museum in New York City's Times Square.
But it wasn't only about flying Old Glory.
Musicians even changed their tunes, and respect for the country's institutions rose. Polls showed Congress, the president and the military all gaining respect. Applications for agencies such as the CIA and FBI rose dramatically.
All over New York volunteers turned out by the thousands to lend a hand. Thousands more showed up at the site and along city roads to cheer on rescue personnel.
"They thought they were going to destroy us," said a New York Fire Department Battalion Commander. "They made this country so strong. It was a renewed patriotism and renewed that, you know, we're good people ... Americans."
About 11 percent of Americans did some form of charity work during the month after Sept. 11. Millions more donated blood, and almost 60 percent donated money -- more than $2.4 billion, to be exact.
These unscripted displays of patriotism reach deep into the heart of our wounded nation even today.
"I have been very uplifted and inspired by the outpouring of patriotism that we have seen over the last year," said Lynn Cheney, wife of Vice President Dick Cheney.
"Many people were surprised I think by the outpouring of what you might call 'spontaneous patriotism,' or patriotism, as I would call it, as a habit of the heart that comes without conscious thought, really," Foner said.
There's the question of what our great nation will look like after the memorials and ceremonies end. Will fewer flags be found flying in neighborhoods and on cars?
"The flags are going to disappear eventually," Foner speculated. "You're never going to have flags all over the place.
"What's wrong with that?" he added. "There's nothing wrong with it, but then it loses its special qualities, so to speak. In other words, then what are you going to do next time?"
Hopefully, there won't be a next time.