The World Trade Center in New York City, United States (sometimes informally referred to as the WTC or the Twin Towers) was a complex of seven buildings in Lower Manhattan, mostly designed by Detroit-based architect Minoru Yamasaki and engineer Leslie Robertson and developed by the Port Authority of New York and New Jersey. It was initiated in 1960 by a Lower Manhattan Association created and chaired by David Rockefeller, who had the original idea of building the center, with strong backing from the then-New York governor, his brother Nelson Rockefeller. The World Trade Center, New York, like most World Trade Centers located around the globe, belonged to the family of World Trade Centers Association. Prior to its destruction, Larry Silverstein held the most recent lease to the complex, the Port Authority having leased it to him in July 2001. The complex, located in the heart of New York City's downtown financial district, contained 13.4 million square feet (1.24 million m²) of office space, almost four percent of Manhattan's entire office inventory at that time

Structural design
The World Trade Center included many structural engineering innovations in skyscraper design and construction. The towers were designed as framed tube structures. There was a frame of closely-spaced columns tied together by deep spandrel beams along the exterior perimeter. The interior had 47 columns, all concentrated in the core. Engineer Felix Samuely used a similar concept in his "Mullion wall" buildings in the early 1950s as did Eero Saarinen in his US Embassy, London (1955-60); but these projects were low to medium rise and may not have been influences.
The perimeter columns supported virtually all lateral loads, such as wind loads, and shared the gravity loads with the core columns. All columns were founded on bedrock, which unlike Midtown Manhattan, where the bedrock is shallow, is at 65 feet (20m) below the surface. Above the seventh floor there were 59 perimeter columns along each face of the building. The perimeter columns had a square cross section, 14 inches on a side (36 cm), and were constructed of welded steel plate. The thickness of the plates and grade of steel were varied over the height of the tower, ranging from 36 ksi to 100 ksi, with the steel strength and plate thickness decreasing with height. The perimeter structure was constructed with extensive use of prefabricated modular pieces, which consisted of three columns, three stories tall, connected together by spandrel plates. The spandrel plates were welded to the columns at the fabrication shop. The modular pieces were typically 52 inches (1.3 m) deep, and extended for two full floors and half of two more floors.
Adjacent modules were bolted together, with the splices occurring at mid-span of the columns and spandrels. The spandrel plates were located at each floor, and served to transmit shear flow between columns, thus allowing them to work together in resisting lateral loads. The joints between modules were staggered vertically, so the column splices between adjacent modules were not at the same floor.
The building's core housed the elevator and utility shafts, restrooms, three stairwells, and other support spaces. The core in 1 WTC was oriented with the long axis east to west, while that of 2 WTC was oriented north to south. The core of each tower was a rectangular area 87 by 135 feet (27 by 41 m) and contained 47 steel columns running from the bedrock to the top of the tower. The columns tapered with height, and consisted of welded box sections at lower floors and rolled wide-flange sections at upper floors. All of the elevators and stairwells were located in the core.

Looking up, 1992
The large, column-free space between the perimeter and core was bridged by prefabricated floor trusses. The floors supported their own weight, as well as live loads, provided lateral stability to the exterior walls, and distributed wind loads among the exterior walls. The floors consisted of 4 inch (10 cm) thick lightweight concrete slabs laid on a fluted steel deck. A grid of lightweight bridging trusses and main trusses supported the floors. The trusses had a span of 60 feet (18.2 m) in the long-span areas and 35 feet (11.0 m) in the short span area. The trusses connected to the perimeter at alternate columns, and were therefore on 6 foot 8 inch (2.03 m) centers. The top chords of the trusses were bolted to seats welded to the spandrels on the exterior side and a channel welded to the core columns on the interior side. The floors were connected to the perimeter spandel plates with vicsoelastic dampers, which helped reduce the amount of sway felt by building occupants. The trusses supported a 4-inch (10 cm) thick lightweight concrete floor slab, with shear connections for composite action.
Hat trusses (or "outrigger truss") located from the 107th floor to the top of the buildings were designed to support a tall communications antenna on top of each building, though only 1 WTC (north tower) actually had an antenna. The truss system consisted of six trusses along the long axis of core and four along the short axis. This truss system allowed some load redistribution between the perimeter and core columns and supported the transmission tower.

Bombing of February 26, 1993
On February 26, 1993 at 12:17 PM, a Ryder truck filled with 1,500 pounds (680 kg) of explosives was planted by Ramzi Yousef and detonated in the underground garage of the North Tower, opening a 100 foot (30 m) hole through 5 sublevels of concrete leaving six people dead and 50,000 other workers and visitors gasping for air in the shafts of the 110 story towers.

Damage underground due to the bombing
Many people inside the North Tower were forced to walk down darkened stairwells which contained no emergency lighting, some taking two hours or more to reach safety. As the Port Authority was a bistate agency, the towers were exempt from New York City building codes. Subsequent to the bombing The Port Authority installed emergency lighting in the stairwells. It is believed that this lighting saved many lives during the events of September 11, 2001.
In 1997 and 1998, six Islamist extremists were convicted and sentenced to life in prison for their roles in the bombing. According to a presiding judge, the conspirators' chief aim at the time of the attack was to destabilize the north tower and send it crashing into the south tower, toppling both landmarks.
As a memorial to the victims of the bombing of the tower, a reflecting pool was installed with the names of those who had been killed in the blast. Following the September 11, 2001 attacks, relief workers found a single fractured piece of the fountain etched with the word "John"; to date it is the only remaining part of the 1993 memorial that survived the collapse of the towers.

Lease
In 1998, plans were approved by the Port Authority to privatize the World Trade Center. In 2001, the Port Authority sought to lease the World Trade Center to a private entity. Bids for the lease came from Vornado Realty Trust, a joint bid between Brookfield Properties Corporation and Boston Properties, and a joint bid by Silverstein Properties and The Westfield Group. By privatizing the World Trade Center, it would be added to the city's tax rolls. The lease was also intended to raise funds for other Port Authority projects. On February 15, 2001, the Port Authority announced that Vornado Trust Realty had won the lease for the World Trade Center, paying $3.25 billion for the 99-year lease.[3 Vornado Really outbid Silverstein by $600 million, though Silverstein upped his offer to $3.22 billion. However, Vornado insisted on last minute changes to the deal, including a shorter 39-year lease, which the Port Authority considered nonnegotiable. Vornado later withdrew and Silverstein's bid for the lease to the World Trade Center was accepted on April 26, 2001, and closed on July 24, 2001.

September 11, 2001
Main articles: September 11, 2001 attacks and Collapse of the World Trade Center

The World Trade Center on fire with the Statue of Liberty in the foreground
On September 11, 2001 at 8:46 a.m. Eastern Time, Al Qaeda suicide hijackers crashed American Airlines Flight 11 into the northern facade of the North Tower. Seventeen minutes later, at 9:03 a.m., a second team of hijackers crashed United Airlines Flight 175 into the South Tower, which collapsed and disintegrated at 9:59 a.m. At 10:28 a.m., the North Tower collapsed and disintegrated. At 5:20 p.m., 7 World Trade Center collapsed as a result of damage from the North Tower's collapse. The four remaining buildings in the WTC plaza sustained heavy damage from debris, and were ultimately demolished.
At the time of the incident, media reports suggested that tens of thousands might have been killed in the massacre, as on any given day upwards of 50,000 people could be inside the towers. Ultimately, 2,750 death certificates were filed relating to the 9/11 attacks, as of May 23, 2007. Of these, 1,614 (59%) were identified from recovered physical remains. 340 Emergency personnel and 60 police officers were killed in the collapse of the Twin Towers. Morgan Stanley was the largest tenant in the World Trade Center, with approximately 2,500 employees in the South Tower and 1,000 in the North Tower. For the following 8½ months, the World Trade Center site cleanup and recovery continued 24 hours a day and involved thousands of workers. The massive pile of debris smoked and smoldered for 99 days.

Notable Events Held
World Chess Championships 1995
In 1995 the PCA world championship, sponsored by Intel, was held between Garry Kasparov and Vishy Anand, ranked first and second in the world. The prize fund was 1,500,000 US$, with 2/3 for the winner.It was staged on the Observation Deck at the 107th floor of the World Trade Center, 400 meters above New York City's financial center Wall Street.

Film and media
The World Trade Center was an iconic structure and has been featured in numerous films, as well as appearing in many television shows, cartoons, comic books, computer/video games and music videos. The events surrounding September 11 are portrayed in several documentaries and movies, including two major motion pictures made in 2006, Oliver Stone's World Trade Center and Paul Greengrass' United 93. Several movies released shortly after 9/11 digitally erased the Twin Towers from skyline shots, such as Spider-Man (film). As of 2007 most reruns of popular television shows have chosen to leave the Twin Towers in airings of the show such as cut scenes in Friends and episodes of The Simpsons. An exception to this, was the opening intro to HBO's Sex and The City, which removed shots of the Towers as a mark of respect for the victims.