After 13 years of planning and over $1 billion in costs, the twin towers debut as the tallest buildings in the world (though they will hold that title only until the completion of the Sears Tower in Chicago in 1974).

Yet surprisingly, space in the 110-story towers, the brainchild of New York financier David Rockefeller and Detroit architect Minoru Yamasaki, does not rent quickly. The addition of 10 million square feet of office space in Lower Manhattan merely exacerbates a pre-existing glut in the commercial real estate market, and because many of the city's financial offices began moving to Midtown in the 1930s, the prospect of a bustling World Trade Center in Lower Manhattan seems unlikely. The Port Authority of New York and New Jersey, the owner of the site, fills much of the north tower with its own offices, while the State of New York occupies the bottom 50 floors of the south tower.

However, thanks to the booming economy of the late 1990s, the financial services industry returns to the area, and by 2001 more than 40,000 men and women work in the World Trade Center each day.

A van loaded with explosives is detonated in the basement of the north tower, killing six people and injuring hundreds more. Later, the bombing is revealed to be the work of Muslim extremists led by Ramzi Ahmed Yousef, a man whose real name, age, and nationality are still unknown. He states at his sentencing in 1998 that the bombing was a response to America's policies toward Palestinians and other Muslims. Yousef and his five accomplices each receive sentences of 240 years in prison and millions of dollars in fines. Though the lower portion of the tower sustains substantial damage, it is quickly repaired and the building reopens a month later.

With demand for office space in the World Trade Center picking up, the Port Authority decides to lease the towers to Larry Silverstein, a private developer who owns the adjacent property at 7 World Trade Center. Silverstein assumes a 99-year lease only six weeks before Sept. 11. He refers to the $3.2 billion deal as "the culminating transaction" of his career, and hires David Childs, of the architectural firm Skidmore, Owings & Merrill (SOM), to begin plans for renovating the public spaces in the towers. Because the deal occurs only weeks before the attacks on the World Trade Center, the insurance policies on the tower have not been finalized, a technicality that will have enormous consequences for Silverstein in the coming months.

At 8:48 a.m., as employees are arriving to work at the trade center, American Airlines Flight 11 flying out of Boston crashes into the north tower. A few minutes later, at 9:06 a.m., United Airline Flight 175, also from Boston, crashes into the south tower. The towers' exterior load-bearing walls allow them to withstand the initial impacts, but their centrally-based exits -- severed in the crashes -- make escape impossible for almost everyone in the floors above the collision. Policemen, firefighters and medical personnel rush to the scene, but at 9:50 a.m. the south tower collapses, followed by the north tower at 10:29 a.m.

A few hundred miles away, American Airlines Flight 77, having just taken off from Washington's Dulles Airport, crashes into the western part of the Pentagon at 9:37 a.m. Meanwhile, the passengers of United Airlines Flight 93 flying over Shanksville, Pennsylvania, attempt to overtake the men who have hijacked their plane, but it crashes suddenly at 10:03 a.m. The attacks, which will later be reported to be work of the terrorist group al Qaeda, take the lives of 2,792 people, including passengers of the hijacked planes, workers in the towers and hundreds of rescue workers.

In the immediate aftermath of the attacks, the nation focuses on grieving, but soon the public begins to wonder about the future of the site: After the debris is cleared, what -- if anything -- should be rebuilt? Who would be in charge of such a massive undertaking, and how would it be paid for? Many vocal groups of victims' families and New York Mayor Rudolph Giuliani argue that nothing should be built where so many people perished. Other groups call for the towers to be put back as they were, to restore New York's landmarks and send a message about America's resolve against terrorism. Still others believe New York has a unique opportunity to build something new and visionary on the site.

As the owner of the 16-acre property, the Port Authority maintains it should decide what is built on the site; Larry Silverstein argues that his lease gives him the right -- even the responsibility -- to rebuild. The state and local governments of New York and New Jersey reason that they should be in charge, since their citizens were killed during attacks on their soil. Lower Manhattan residents from Tribeca, Chinatown and Battery Park City clamor to be involved in the decision-making, since any development at Ground Zero will directly affect their quality of life. And of course, the victims' families feel they have a stake in the future of the site. However, no precedent exists for a public building process involving so many stakeholders.

Governor George Pataki of New York and outgoing New York Mayor Rudolph Giuliani join forces to form a new public agency dedicated to the rebuilding of Lower Manhattan in "an open, inclusive, transparent manner." The new agency, the Lower Manhattan Development Corporation (LMDC), ultimately consists of a 16-member board selected by the governor and the mayor and is charged with overseeing all developments at the site. In the fall and winter of 2001, its ranks expand to include some of the most respected and influential people in New York business, city planning, and politics. John C. Whitehead, the former co-chairman of Goldman Sachs, is named the new chairman of the LMDC board. Other board members include Dick Grasso, the chairman of the New York Stock Exchange (who later resigns from the NYSE and the LMDC after a scandal involving his NYSE compensation) and Roland Betts, a real estate developer and close friend of President George W. Bush.

Though it is still uncertain who has the authority to rebuild, several groups hold public meetings in the winter of 2002 to discuss the future of the site. The LMDC holds its first meeting on Jan. 29, but discussion quickly becomes a laundry list of complaints and unfocused desires. Then in February, New York New Visions, a coalition of 350 architects and design professionals, holds a meeting to discuss its ideas for the future of downtown. A third group also becomes involved in the planning: the Civic Alliance to Rebuild Downtown (known as the Civic Alliance), an umbrella group of civic associations, including the American Institute of Architects and the Municipal Art Society. On Feb. 7, the Civic Alliance holds an event called "Listening to the City," a modern take on the old-style town hall meeting. Hundreds of participants attend and are asked to respond to several questions by computer so that the results can be tallied instantly.

Though none of these groups have the authority to rebuild Ground Zero, consensus emerges from their discussions that will be hard for the developers and architects to ignore. They call for transparency in the selection of a memorial; a new, mixed-use plan for the neighborhood; improved public transportation; a stronger connection with the tri-state region; high quality architecture; an inclusive planning process; the restoration of the original street grid that was lost when the original World Trade Center was built; and the restoration of the New York City skyline.

Six months after the attacks, an interim memorial is installed at Ground Zero. For one month, two "Towers of Light" illuminate the space in the sky where the trade towers once stood.

Also in March, the Port Authority and the LMDC strike a deal about the program for the 16-acre Ground Zero site. The Port Authority had originally rejected the notion that anything should be built on the site other than the 10 million square feet of office space and the shopping center that had been there before Sept. 11, while the LMDC envisioned a substantially different space that would include cultural and memorial facilities, perhaps even some housing. The organizations work out a "memorandum of understanding" in which the LMDC promises not to impose its program on the Port Authority in exchange for a leading role in the selection of the architectural designs. The Port Authority, in turn, agrees to build memorial and cultural facilities on the site.

The Port Authority asks several architectural firms to submit proposals for the World Trade Center site. The Port Authority's architectural program is densely packed with its own requirements and those of the LMDC, including: 11 million square feet of office space; 600,000 square feet of retail space; a hotel; a transportation hub; cultural and civic institutions; off-site housing; large public spaces; and a permanent memorial. Because it incorporates the views of so many stakeholders, the program is heralded as the successful result of inclusive city planning, but it is also a recipe for trouble. Any submission that meets all of the requirements will have to emphasize practicality at the likely expense of imagination.

The LMDC and the Port Authority review proposals from 15 architectural firms and in May, they select the Manhattan firm of Beyer Blinder Belle, led by partner Jack Beyer, to design six different concepts for the site.

On July 16, Beyer Blinder Belle unveil their six plans for Ground Zero at a press conference in Lower Manhattan. Both public and critical reaction to them is cool. The Civic Alliance, partnered this time with the Port Authority and the LMDC, holds a second "Listening to the City" meeting just four days later. This time over 4,000 people attend, and many complain that the designs are lacking in vision, are too similar to each other, and fail to appropriately memorialize the tragedy of Sept. 11. The public demands that all six plans be scrapped and new proposals be considered.

The LMDC responds to the uproar over the initial designs by issuing a request for new master plan proposals and by giving architects a less restrictive architectural program than it did for the initial proposals. It stipulates only that the designs provide "a tall symbol or structure that would be recognized around the world;" avoid building on the footprints of the previous towers; restore portions of the street grid; consider building housing on the site; connect Battery Park City to Ground Zero; and provide a central train station, cultural facilities, public spaces, and commercial and retail space. The LMDC names the project the "Innovative Design Study" in an attempt to distinguish it from the unpopular Beyer Blinder Belle proposals and to make it clear that they are not holding a "design competition" -- though the LMDC may select a design, it will not have final say over exactly what is built on the site.

On Sept. 8, just days before the first anniversary of the attacks, Herbert Muschamp, architecture critic for The New York Times, publishes his own study for Ground Zero in The New York Times Magazine: a collection of daring designs by 12 of the world's most famous architects. Muchamp titles his article "Don't Rebuild, Reimagine," a challenge to the Port Authority and the LMDC to consider something more avant-garde than its current program for the site.

Meanwhile, seven teams of architects from a pool of over 406 submissions from around the world are selected to participate in the LMDC's Innovative Design Study: British lord and architect Norman Foster; THINK Design, a consortium of international architects lead by Rafael ViÒoly; another group of internationally renowned architects named United Architects; a team from SOM lead by Roger Duffy; a group of eminent New York architects including Richard Meier, Charles Gwathmey, Peter Eisenman and Steven Holl; and Daniel Libeskind, an American architect best known for his Jewish Museum Berlin. Each team is given a small stipend of $40,000 and three months to develop models and images of their designs.

On Dec. 18, thousands of people attend the unveiling of the Innovative Design Study at a press conference in the Winter Garden, a glass atrium in the World Financial Center, across the street from Ground Zero. The entire three-hour event is broadcast live on several television stations and on the LMDC Web site. This time, both public and critical reception is enthusiastic. All the plans are put on view in the Winter Garden and the LMDC Web site. Over 100,000 people visit the exhibit at the Winter Garden, and over 6 million people visit the LMDC Web site.

On Feb. 4, the LMDC announces two semi-finalists in its Innovative Design Study: the THINK team lead by Rafael ViÒoly and Daniel Libeskind of Studio Daniel Libeskind. Over the course of the next few weeks, the teams will revise their plans and present them to the public at meetings with civic and community groups and on several national television shows including the Today Show and the Oprah Winfrey Show.

On Feb. 26, just a day before the winner is to be announced, an article in The New York Times reveals that the jury has voted in favor of the THINK team's plan. However, Governor Pataki and Mayor Bloomberg have yet to weigh in and they voice their support for the Libeskind plan, which is announced as the official winner the following day. Libeskind is ecstatic, commenting, "I wanted to make a site for the greatest memorial the world has ever seen." But though Libeskind included designs for a memorial and a tower in his site plan, it is uncertain that they will be built to his specifications. Only Larry Silverstein, who is awaiting the settlement of several billion dollars in insurance claims, has the money or clear legal authority to rebuild, and he has retained David Childs for the project. Without committing to building the Libeskind tower, Silverstein appears enthusiastic about the LMDC's choice of a master plan: "[They] picked the right one."

In May, Silverstein formally announces that David Childs of SOM will design the new Freedom Tower, as it was dubbed by Governor Pataki in April. Silverstein adds that Daniel Libeskind "will be a part of the team of architects" and that Childs' tower "will reflect the spirit of Dan's site plan."

Meanwhile, the LMDC launches an international design competition to select an architect for the 9/11 memorial. In all, more than 13,000 entries are submitted from 94 nations and all 50 states.

Despite the expectation that Childs and Libeskind will work together on a single design for the tower, the two work separately and design two very different buildings. To complicate matters, each tower has a claim as the "official" design -- Childs' because it has the backing of Larry Silverstein, and Libeskind's because it has the backing of the governor.

After an all-night meeting at LMDC headquarters on July 15, Kevin Rampe, president of the LMDC, gets the two architects to hammer out an agreement: David Childs will serve as "Design Architect and Project Manager" on the tower, and Daniel Libeskind will be a "collaborating architect during the concept and schematic design phases."

By fall, it is clear that the partnership is not working out: Childs is designing a building with key components that diverge sharply from Libeskind's site plan. Libeskind's master plan had specifically called for a tower at the symbolic height of 1,776 feet with a spire that mirrored the raised torch of the Statue of Liberty. Childs proposes a much more symmetrical, torqued and tapered building some 2,000 feet high and without the symbolic spire.

Yet none of this is presented to the public at the LMDC's press conference to unveil Libeskind's "Refined Master Plan" on Sept. 17. Although the site plan has been changed to resolve layout issues involving transportation networks and commercial and public space, the Freedom Tower looks just as it did the day Libeksind won the competition.

On Oct. 23, The New York Post breaks the story that the two architects are in a fierce battle with Libeskind threatening to walk away from the project if Childs does not redesign his tower to fit Libeskind's site plan. According to The New York Times, Pataki informs Silverstein that he wants to see in Childs' design "something like Mr. Libeskind's asymmetrical Freedom Tower, with its visual reference to the upraised arm of the Statue of Liberty."

Five days later, Silverstein meets with Childs and Libeskind at his office and tells the two architects they will have to reach a compromise. The final design, he says, will have to make use of the technical work already done by the SOM team and conform to the four main principles of Libeskind's site plan: that it have an asymmetrical spire, reach 1,776 feet, mark the slurry wall that was the foundation of the original towers, and be the apex of a series of towers at the site.

In early November, Libeskind and Gov. Pataki are shown Childs' revised design: a 2,000-foot superstructure consisting of a 1,776-foot office building capped by a 224-foot spire. Both Libeskind and Pataki seem pleased with the concept. According to The New York Times, Libeskind calls the design "ingenious" at the time and particularly admired its torqued shape and windmill garden, which he feels is in keeping with the ecological theme he set in his master plan. But neither he nor Pataki sees the model in the context of the overall site plan, and later Libeskind worries that the tower may be out of proportion to its surroundings.

But Libeskind could not make his case that Childs' tower was too tall because he did not have access to scaled renderings of it. According to accounts that appeared in The New York Times and The New York Post, on the night of Dec. 4, several staff members from Studio Daniel Libeskind arrive at SOM's office, where they had been working for several weeks, and despite the objections of SOM staff members, remove copies of the most recent computer renderings of Childs' tower.

The next day in a meeting with members of Pataki's staff, Libeskind uses the materials taken from the SOM office to make his case that Childs' tower is out of proportion with the rest of the site. The governor's staff agrees with Libeskind, and Childs is told to reduce the tower to 1,600 feet.

On Dec. 8, at what is intended to be a crucial design meeting between the two architects, Libeskind arrives with his lawyer, Ed Hayes, and states that he will not give his approval to any tower that is more than 1,776 feet tall. Janno Lieber, Silverstein's project director, cuts the meeting short, declaring that he won't negotiate the tower's design through lawyers. Lieber then calls a meeting with Hayes and LMDC President Kevin Rampe to discuss the impasse. Hayes insists that the tower must conform to his client's design and calls Pataki's chief of staff to "back [Libeksind] up."

At Pataki's insistence, Childs designs a 1,600-foot building, topped by a spire that reaches 1,776 feet, but Libeskind worries that a spire only 176 feet tall will look "stubby, more like a pinky finger than the torch-bearing arm of the Statue of Liberty." Libeskind suggests the tower be shortened to 1,450 feet, but Childs rejects the idea.

Still at an impasse, Pataki meets with both parties at state offices on Dec. 12 and instructs Childs to lower the roof of his design over the weekend to 1,500 feet, thus increasing the height of the spire to 276 feet.

On Dec. 18, the day before the public unveiling of the tower, Libeskind sees the revised design and gives it his "provisional" approval. The next day, four days behind schedule, the new Freedom Tower is shown to the public at a press conference attended by the principal players: Childs, Libeskind, Pataki, Bloomberg, and Silverstein. Governor Pataki calls the revised tower "a symbol of New York. A symbol of America. A symbol of freedom." Libeskind's statement at that press conference suggests that a consensus had been reached, even though it had not been an easy collaboration: "David Childs and SOM have responded to the aspirations of the master plan, giving form to the Freedom Tower whose principals are rising to the symbolic height of 1,776 feet, echoing the Statue of Liberty and completing the spiraling composition of the towers on the site". Childs also alludes to the conflict during an appearance on the Today show. "Creative minds have different thoughts about how you do things," he said. "That's what makes great architecture. I wouldn't want to work with somebody who would just say, 'Yes.' And I think Danny feels the same way."

On Jan. 6, the LMDC announces that its 13-member jury has selected "Reflecting Absence," by Michael Arad and Peter Walker, as the winner of the World Trade Center Memorial Competition. Although the memorial design conforms to Libeskind's site specifications, two fountains will subsume the footprints of the towers, and a raised garden will cover the exposed slurry walls -- both features that were central to Libeskind's original design. Despite these changes, Libeskind states that the voids represented by the memorial fountains have a "meaningful connection" to his master plan.

Libeskind's original plan is further altered in late January, when Santiago Calatrava's design concept for the new PATH transportation hub is unveiled. The height of the station will alter Libeskind's original Wedge of Light Plaza by obscuring the path of sunlight that was supposed to illuminate the park every Sept. 11.

In early May, Silverstein's lawsuit against his insurance agency fails, significantly reducing the amount of funds he will have available for rebuilding at Ground Zero. Though he insists he has enough money to pay for the Freedom Tower himself, he will have to seek conventional loans from financial institutions to pay for the other three office towers on the site slated to be built by the superstar architects Norman Foster, Jean Nouvel, and Fumihiko Maki.

In late May, Libeskind files a lawsuit against Silverstein for payment he claims he is owed for his contribution to the Freedom Tower. Libeskind submits a bill for $800,000, but Silverstein agrees to pay only $125,000, arguing that Libeskind has already been paid $2.25 million by the LMDC for his master plan. The dispute is a result of Silverstein's request that Studio Daniel Libeskind submit timesheets for the firm's work on the tower. Libeskind claims he does not normally keep timesheets, but he would have had Silverstein asked at the beginning of the project.

Gov. Pataki pushes to begin construction before the Republic National Convention arrives in New York City in August 2004, and on July 4 -- Independence Day -- workers lay the cornerstone for the foundation of the Freedom Tower. It is made of a speckled block of granite from the Adirondack Mountains that measures five and a half feet high and weighes 20 tons. The cornerstone is engraved in a simple font called "Gotham" that was invented by a New York native. It reads: "To honor and remember those who lost their lives on September 11, 2001, and as a tribute to the enduring spirit of freedom, July Fourth 2004."