As the charred remains of steel, concrete and Indiana limestone were being removed from the Pentagon crash site after Sept. 11, 2001, officials set an ambitious goal: staff would be back in their offices in the most severely damaged areas exactly a year after the attack.

They beat that goal by nearly a month, after around-the-clock construction and a sense of pride and purpose that permeated every layer of the project, along with a lack of Washington bureaucracy.

A two-acre public memorial honoring the 184 people killed that day, is taking longer, however.

When the hijacked plane plowed into the Pentagon, the building was in the midst of a 20-year, $1.2 billion renovation.

Amazingly, the terrorists guided the plane into the one "wedge" that had been renovated and sliced diagonally through a part of both the new and old building. Project engineers said the death toll would have been much higher if it were not for some of the improvements, such as state-of-the-art blast-resistant windows, polymer mesh-reinforced walls to prevent pieces from flying off like deadly shrapnel, and sprinkler systems.

Still, fire fed by 10,000 gallons of jet fuel damaged 2 million square feet of the Pentagon -- almost a third of the building.

Lee Evey, the renovation program manager, said there were people at the Pentagon who rushed to the crash site and immediately began to put together a team for the recovery and reconstruction.

"We went out and we hired very, very quickly, overnight, some people who are experts in blast recovery. They had worked Mexico City, they had worked Oklahoma City, they had worked the earlier blast at the Twin Towers in New York, and got them on site as quickly as possible," he told the NewsHour in January 2002.

After all the human remains that could be found were recovered, construction workers set to work, launching what became known as the Phoenix Project. In response to calls for a concrete goal, project managers erected a clock that counted down to Sept. 11, 2002.

Pentagon employees began to return to their offices as early as August 2002, and the Phoenix Project officially came to an end in February 2003, when the last tenants moved back into areas of "Wedge 1" destroyed in the attack. Workers did in less than a year what it had taken them three years to do previously.

The head of the unprecedented reconstruction effort was Alan Kilsheimer, a structural engineer with years of experience in blast recovery who arrived on site the afternoon of Sept. 11. He was called to New York for the Trade Center site, but he lived in Washington, and when he heard that another plane had hit the Pentagon, that's where he went.

Kilsheimer, a bearded, irreverent visionary was paired with the clean-cut and buttoned down project manager for the Pentagon, Will Colston. Together, they were able to cut through red tape and inspire a motley collection of contractors for the unprecedented task.

In the first stage, demolition crews working around the clock, refusing to take holidays or weekends, flattened and removed 400,000 square feet of the damaged building. Instead of the estimated six months, the demolition phase took a month and a day.

"The next guy tried to beat his own schedule by more than that guy beat his schedule, and that's how it happened. Every person is showing what can be done," Kilsheimer told the NewsHour in 2002.

The "let's do this" spirit extended far from the construction site along the Potomac. Kilsheimer was worried about getting limestone for the exterior, because the quarries would be closing for the winter. They contacted Bybee Stone Co. in Indiana, the source of the original Pentagon limestone, and asked them to quarry many blocks. Bybee called back a day later and told him not to worry, the company would work through the winter, The Washington Post reported.

The rebuilt section of the Pentagon is tougher and has pervasive safety features. Firewalls prevent flames and smoke from spreading. New windows have two-inch thick glass encased in interlocking steel-beam supports, interspersed with an experimental Kevlar bullet-proof cloth and moveable walls to prevent cave-ins in case of an explosion.

Small changes also came from lessons learned from the attack, including the installation of luminescent strips that show people the way out and exit signs on the floorboards -- black smoke concealed the regular markers that day.

The Pentagon is continuing renovation beyond its original scope of reinforcement work to add new amenities for building workers, including a proposed conference center and a $40 million athletic center with an auditorium and television studio by December 2012.

A new Pentagon bus station -- the region's largest bus-to-rail transfer station -- opened three months after the attack as planned. New bays were moved an additional 10 feet away from the building to 280 feet. The escalator leading into the concourse was closed and security was vastly improved.

But for the men and women who worked on Project Phoenix, the period between September 2001 and September 2002 belongs in the history books.

"This is the single most incredible construction thing that's happened in this country that any of us know about, as far as what has been done by these 2,900 people and how they put it together. And I don't know, hopefully would never have to be done again, but I don't know that it could ever be done again," Kilsheimer said as the project came to and end.

While the portions of the Pentagon destroyed on Sept. 11 are completely rebuilt, plans for a permanent memorial are progressing more slowly as designers, engineers and family members work carefully to properly memorialize the lives lost in the day's devastating events.

The winning design was chosen from a competition announced soon after the attacks.

Six finalists were selected from more than 1,100 entries. In March 2003, a jury composed of design and engineering experts and victims' family members picked the winning design: the vision of New York architects Julie Beckman and Keith Kaseman.

"When we learned of the Pentagon Memorial Competition ... we felt a natural obligation to contribute whatever we could to the discussion at hand. For several weeks, we consistently talked about ... a space that would respectfully engage one's intellect on infinitely interpretive levels -- as one family member poignantly stated, the Memorial should 'make people think,' but 'not tell them what to think,'" the designers said in a statement.

Beckman and Kaseman's design, called "Light Benches," imagines 184 benches, one dedicated to each victim, positioned according to the victims' ages -- from 3 to 71. Each will hover above a reflecting pool and the site will be shaded with 80 paperbark maple trees, which were chosen because they keep their leaves late into the autumn.

The benches will be made of an alloy called super duplex stainless steel. "It has a life span that will go well beyond 100 years," Kaseman told The Washington Post. "It will look exactly the same more than 100 years from now as it does the day the memorial opens."

The alloy was used in the reconstruction of the Statue of Liberty and is used in catapults on aircraft carriers, which are subjected to corrosive conditions.

Architecture critics such as the Post's Benjamin Forgey said the benches made the memorial stand out from the competition.

"Probably the most unusual aspect of the design is the shape of the benches, which the designers refer to as 'memorial units,'" Forgey wrote in March 2003.

"Rather than the conventional long seat with supports at two ends, these resemble diving boards, with a rigid cantilevered seat extending about six feet from a heavy base. Underneath the cantilevered seat of each bench will be a narrow pool of water," Forgey wrote.

Fifty-nine benches will face one direction and 125 will face the other, to distinguish between victims aboard Flight 77 and those who were inside the Pentagon. The memorial will be built on nearly two acres of land in parallel lines marking the passenger jet's final path before it hit the building.

About $10.8 million has been raised for construction of the memorial, whose cost has risen from $18 million to $22 million. The money has come from everything from neighborhood lemonade sales to corporate and personal donations, according to the Post.

The memorial is expected to be completed by September 2008.

-- Compiled by Leah Clapman for the Online NewsHour