Before the dust had even settled at ground zero, the losses were staggering: nearly 3,000 people were dead. Four jetliners were gone, and buildings once tall and strong lay in tragic ruin.
In the nation's response to 9/11, the costs would continue to grow, "Early Show" co-anchor Chis Wragge observed Friday.
"The United States has spent to date about $2.3 trillion," says Neta Crawford, a professor of political science and African-American studies at Boston University.
The Department of Homeland Security was created and took over the screenings at all the nation's airports.
There was new funding for intelligence and for the State Department. But by far, most of the money has gone to pay for war: $1.3 trillion, so far, to fight in Iraq and Afghanistan.
"More than $800 billion in Pentagon direct spending has gone toward the war in Iraq," Crawford says.
That's a far cry from the Bush administration's early estimates of between $50 billion and $60 billion.
Of course, the biggest cost can't be measured in dollars and cents: the human toll.
There have been more than 180,000 civilian casualties in Iraq and Afghanistan. Nearly 70,000 allied troops have been wounded, and more than 6,000 U.S. servicemen and women have died.
First Lt. Colby Umbrell is one. His parents, Nancy and Mark, miss him every day.
"I'm glad at least we had the 26 years, because he's an awesome guy," said Nancy Umbrell.
Colby Umbrell grew up in the suburbs of Philadelphia. He was an athlete, a runner and a football player. He loved kids -- he was a swimming coach for the Special Olympics. And he was a soldier. Six feet tall, 245 pounds and square-jawed, he looked every bit the part.
"When he decided to do something, he did it 100 percent. That makes us very proud and it makes us smile now," said Nancy Umbrell.
In the spring of 2007, Colby Umbrell was leading his men on a routine patrol when a roadside bomb ripped through his hum-vee.
"I was at home by myself, and I saw the car pull up and you see two men in uniform and you pretty much know," Nancy Umbrell recalled.
It wasn't until the burial that Nancy Umbrell says her son's death became real to her. On May 18, 2007, the Umbrells laid Colby to rest in section 60 of Arlington National Cemetery.
"I can't describe to anybody what it is to bury your child," said a teary Nancy Umbrell, "and then the days, like I said, when you don't want to wake up."
The Umbrells say they know Colby is, in a way, a casualty of the terror attacks of 9/11. But they also know their son always wanted to be a soldier.
"We wouldn't have changed anything," Nancy Umbrell points out. "It keeps us from getting angry. I miss him, but I'm very proud of him."