(Image source: Camilo Jose Vergara)

BY TRACY PFEIFFER

ANCHOR EMILY SPAIN

September 11th, 2001, saw the worst terrorist attack on U.S. soil in the country’s history.

The assault that brought down the World Trade Center’s Twin Towers and Flight 93 and struck the side of the Pentagon in Pennsylvania left almost 3,000 people dead.

And a decade later-- the effects of that day are still strong in the American psyche.

In his weekly radio address, President Barack Obama encouraged unity.

PRES. BARACK OBAMA: “We are Americans, and we are stronger and safer when we stay true to the values, freedom, and diversity that makes us unique among nations. …Ten years ago, ordinary Americans showed us the true meaning of courage when they rushed up those stairwells, into those flames, into that cockpit. In the decade since, a new generation has stepped forward to serve and keep us safe. In their memory, in their name, we will never waver.”

A NASA astronaut -- who was commander of the International Space Station at the time -- took photos of the New York attack from space-- and reflected on his experience.

FRANK CULBERTSON, EXPEDITION 3 COMMANDER: “I didn’t know exactly what was happening, but I knew it was really bad because there was a big cloud of debris covering Manhattan.”

CULBERTSON (2001): “We flew past New York City and saw the effects of that attack on New York City.”

CULBERTSON (2011): “That’s when it really became painful, because it was like seeing a wound in the side of your country, of your family, your friends.”

Some-- are taking a look back at the iconic towers themselves.

Construction on the World Trade Center complex began in the 60s-- and it opened in 1973.

The Christian Science Monitor reports-- the Center’s Twin Towers weren’t always a beloved part of the New York skyline. (Images: Camilo Jose Vergara)

“With their sleek lines and audacity to rise a quarter-mile into the sky, the towers did eventually win the adoration of most of New York and her visitors. Who among us has watched a pre-9/11 movie and not felt a stab upon seeing the New York skyline with the two iconic sentinels intact?”

And New Jersey’s Star-Ledger recalls just how impressive the buildings were.

“Skyscrapers had topped out in 1931 with the Empire State Building’s 102 floors. This limit, which had prevailed for 40 years, was based on accepted engineering practice. ...Each of the towers’ 110 stories was nearly an acre. They married 200,000 tons of steel, 425,000 cubic yards of concrete, more than 43,000 windows, 198 miles of heating and cooling ducts, 12,000 miles of electric cables and more than 100 elevators.”

And in a piece for The Huffington Post, actress Tina Sloan writes-- even more iconic than the Towers, were those who stepped up to save lives even as the buildings were coming down.

“...we started hearing about the Heroes. The Heroes who stood as tall as those Twin Towers once were, who filled the desolate space at the World Trade Center with their incredible bravery, their immense compassion, and sometimes with their lives. They stand where The Towers once stood in our minds.”

And from New York, to Pennsylvania-- where a memorial to the passengers of Flight 93 was opened in the town of Shanksville.

Among the speakers-- Vice President Joe Biden and former presidents Bill Clinton and George W. Bush.

Here’s MSNBC with Bush’s address.

GEORGE W. BUSH, 43RD PRESIDENT OF THE UNITED STATES: “September the 11th, 2001, innocent men and women went to work at the World Trade Center. They reported for duty at the Pentagon. They boarded American flights 11 and 77, United flights 93 and 175. …One of the lessons of 9/11 is that evil is real, and so is courage.”

The 1 World Trade Center Memorial Plaza opened for the anniversary, but construction on the rest of it -- including the Freedom Tower --  is scheduled through 2013.