7 World Trade Center (1987–2001)
| Industry | Real estate, office building |
|---|---|
| Founded | May 1987 |
| Founder | Larry Silverstein |
| Defunct | September 11, 2001 |
| Fate | Destroyed during the September 11 attacks |
| Successor | 7 World Trade Center (2006) |
| Headquarters | New York City , United States |
Key people | Larry Silverstein (developer) |
| Products | Office rental space |
| Owner | Larry Silverstein (under ground lease with Port Authority of New York and New Jersey) |
7 World Trade Center (also referred to as 7 WTC, WTC-7, or Tower 7), and sometimes called Building 7 or the Salomon Brothers Building, was an office skyscraper within the original World Trade Center Complex located in Lower Manhattan, New York City. Positioned on a site bordered by West Broadway, Vesey Street, Washington Street, and Barclay Street, the property was developed by Larry Silverstein under a ground lease agreement with the Port Authority of New York and New Jersey. Its architectural design was executed by Emery Roth & Sons. The tower was ultimately destroyed during the September 11 attacks as a result of structural impairments and fires. The final collapse, which lasted approximately 5.4 seconds, included about 2.25 seconds of free-fall acceleration, as documented in the concluding report by the NIST.
The initial 7 World Trade Center comprised 47 floors, featured a red granite exterior, and had a trapezoidal base shape. An elevated pedestrian bridge spanned Vesey Street, linking it directly to the World Trade Center plaza. Constructed atop a Consolidated Edison electrical substation, the building faced distinctive engineering challenges. Completed in 1987, it secured Salomon Brothers as its principal tenant through a long-term leasing agreement finalized in 1988.
On September 11, 2001, falling debris from the collapse of the nearby North Tower inflicted severe damage to the building, causing fires across several lower floors. These fires burned unchecked due to inadequate water pressure within its fire suppression system. The collapse initiated when a vital internal column failed, precipitating a progressive failure of adjacent columns. The initial visible external indication was the disintegration of the rooftop penthouse at 5:20:33 pm, leading to a full collapse around 5:21 pm according to FEMA, while NIST recorded the final collapse time as 5:20:52 pm. This event represented the first recorded case of a steel-framed high-rise succumbing primarily to uncontrolled fires. A replacement structure on this location was completed and opened in 2006.
Architecture
The original 7 World Trade Center was a 47-story structure designed by Emery Roth & Sons, distinguished by its red granite exterior. It rose to a height of , featuring a trapezoidal footprint measuring by .Tishman Realty & Construction oversaw its construction process.
Mechanical features
Constructed above a two-story electrical substation operated by Con Edison since 1967, 7 World Trade Center incorporated unique foundational elements. The substation’s caisson foundation was initially engineered to support a 25-story building with . However, accommodating a larger building required implementing gravity column transfer trusses and girders between floors five and seven to redirect structural loads onto the smaller existing foundation. Original caissons from 1967 were augmented with additional ones, while the fifth floor functioned as a structural diaphragm enhancing lateral stability. Above the seventh floor, the building utilized a conventional tube-frame system consisting of core and perimeter columns combined with moment frames designed to resist lateral forces.
A shipping and receiving ramp servicing the entire World Trade Center complex occupied roughly one-quarter of the building’s eastern footprint, allowing truck clearance beneath up to the third floor. Structural steel components were protected with gypsum-based Monokote fireproofing material rated for two hours on beams, girders, and trusses, and three hours on columns.
Mechanical equipment spanned floors four through seven and included twelve transformers located on the fifth floor. Multiple emergency generators provided backup power for tenants such as New York City Emergency Management and Salomon Brothers. To fuel these generators, an underground storage facility held approximately 24,000 gallons (91,000 liters) of diesel fuel, with fuel distribution systems extending from ground level up to the ninth floor. The rooftop contained two mechanical penthouses—a smaller one on the west side and a larger one on the east side.
Office Spaces
Each level provided expansive rentable office areas, with 7 World Trade Center's floor layouts considerably exceeding the size of typical urban office buildings. The entire structure encompassed a total of 1,800,000 square feet dedicated to office use. Two pedestrian bridges linked the building’s third floor to the main World Trade Center complex across Vesey Street. The lobby was adorned with distinguished artworks, notably featuring a large mural by Al Held entitled The Third Circle.
Historical Background
Construction commenced on October 2, 1984, and the building officially opened in May 1987 as an integral part of the World Trade Center complex.
In June 1986, developer Larry Silverstein secured Drexel Burnham Lambert as the sole tenant under a $3 billion, 30-year lease agreement for the entire building. However, following Drexel’s insider trading scandal in December 1986, this lease was terminated, prompting Silverstein to pursue alternative tenants. Spicer & Oppenheim leased approximately 14% of the available space, but due to economic downturns including the 1987 Black Monday crash, a significant portion of the building remained unoccupied until rental rates were lowered by April 1988.
By November 1988, Salomon Brothers abandoned plans for a Midtown development and instead signed a 20-year lease for the top 19 floors. To accommodate Salomon Brothers’ trading operations, extensive renovations took place in 1989 involving the removal of three floors and reinforcement with over 350 tons of steel to create double-height trading floors. Backup power was ensured by installing nine diesel generators on the fifth floor. Silverstein described this process as constructing "a building within a building," allowing for flexible interior layouts without compromising structural strength.
Following the February 1993 World Trade Center bombing, New York City Mayor Rudy Giuliani designated 7 World Trade Center as the site for an emergency command center and installed related fuel tanks there. Despite controversy after the September 11 attacks, investigations determined that these fuel tanks did not contribute to the building’s collapse.
Tenants at Closure
At the time of the September 11 attacks, Salomon Smith Barney was the predominant occupant in 7 World Trade Center, leasing approximately 64 percent of the space across floors 28 through 45. Other significant tenants included ITT Hartford Insurance Group (122,590 square feet), American Express Bank International (106,117 square feet), Standard Chartered Bank (111,398 square feet), and the Securities and Exchange Commission (106,117 square feet). Smaller occupants comprised the Internal Revenue Service Regional Council (90,430 square feet) and the United States Secret Service (85,343 square feet). Among the smallest tenants were the New York City Office of Emergency Management, National Association of Insurance Commissioners, Federal Home Loan Bank of New York, First State Management Group Inc., Provident Financial Management, and the Immigration and Naturalization Service. The Department of Defense and Central Intelligence Agency shared space on floor 25 alongside the IRS; notably, the CIA's presence was only revealed following September 11. Mechanical equipment occupied floors 46–47 as well as the first six floors and part of floor seven.
According to CoStar Group data, floors 9 and 10 were utilized by the Secret Service. The CIA maintained offices on floor 25. The National Institute of Standards and Technology's 2008 Final Report on the Collapse of World Trade Center Building 7 confirmed that floor 14 was vacant at that time and updated records to indicate Salomon Smith Barney leased floors 15 through 17.
The following table summarizes leased space by tenant:[1][2][3]
| Tenant | Leased Area (sq ft) | Floors Occupied | Sector |
|---|---|---|---|
| Salomon Smith Barney | 1,202,900 | G–6,13,15–24,26–47 | Financial Services |
| Internal Revenue Service Regional Council | 90,430 | 24–25 | Government |
| United States Secret Service | 85,343 | 9–10 | Government |
| American Express Bank International | 106,117 | 7–8,13 | Financial Services |
| Standard Chartered Bank | 111,398 | 10,13,26–27 | Financial Services |
| Provident Financial Management | 9,000 | 7,13 | Financial Services |
| ITT Hartford Insurance Group | 122,590 | 19–21 | Financial Services |
| First State Management Group | 4,000 | 21 | Insurance |
| Federal Home Loan Bank | 47,490 | 22 | Financial Services |
| National Association of Insurance Commissioners Securities | 22,500 | 19 | Insurance |
| Securities & Exchange Commission | 106,117 | 11–13 | Government |
| New York City Office of Emergency Management | 45,815 | 23 | Government |
Collapse
When the North Tower (1 World Trade Center) fell on September 11, 2001, substantial debris impacted 7 World Trade Center, damaging its southern exterior and sparking fires that raged through the afternoon. The collapse inflicted harm on the southwest corner between the 7th and 17th floors, as well as the south facade from the 44th floor up to the roof. Additional structural impairments included a significant vertical tear near the center of the south face spanning floors 24 to 41. Although a sprinkler system was installed, it had limitations: fire pumps required manual activation, floor-level controls connected only once to the sprinkler riser, and water pressure was insufficient, all of which hampered firefighting efforts.
After the North Tower’s collapse, firefighters entered 7 World Trade Center to locate and extinguish fires but struggled due to inadequate water pressure. Fires spread uncontrollably across several floors—particularly between floors 7 and 9 and floors 11 to 13—and were clearly visible on the building’s eastern side. Around 2:00 p.m., responders noticed a bulge forming in the southwest corner between floors 10 and 13, signaling structural instability. Throughout the afternoon, creaking noises were reported. By roughly 4:00 p.m., FDNY Chief of Operations Daniel A. Nigro ordered evacuation of the vicinity over safety concerns.
The intensifying fires led to failure of key girders, causing buckling of a critical northeast corner column (Column 79) below floor 13. This initiated collapse of upper levels down to a transfer floor at level five. Cracks appeared in the facade moments before complete failure. According to FEMA, collapse commenced at 5:20:33 p.m. EDT with disintegration of the east mechanical penthouse; exact times vary slightly by source but full collapse occurred around 5:21 p.m. EDT.
No fatalities resulted from this collapse. Investigations by NIST found no proof supporting explosive conspiracy theories; instead, a combination of physical damage, uncontrolled fires, and the building’s distinctive design caused a progressive structural failure.
Reports
In May 2002, the Federal Emergency Management Agency (FEMA) released an initial report on the collapse under Dr. W. Gene Corley, P.E., concluding that fires ignited by debris from Towers 1 and 2 were primarily responsible. These fires burned unchecked due to lack of water supply for sprinklers or firefighting efforts. However, the report did not definitively determine the precise cause and recommended further study.
The National Institute of Standards and Technology (NIST) was authorized to conduct an extensive investigation into structural failures of both Twin Towers and 7 World Trade Center.[4] Led by Dr. S. Shyam Sunder, NIST collaborated with professional bodies such as the Structural Engineering Institute of the American Society of Civil Engineers (SEI/ASCE), Society of Fire Protection Engineers (SFPE), among others.[5]
Investigation into 7 World Trade Center was postponed until completion of Twin Towers’ reports.[4] NIST issued a preliminary report in June 2004 followed by periodic updates.[6] From June 2004 through September 2005, staff assigned to 7 WTC were redirected full-time to Twin Towers investigations.[7] In June 2007, Sunder acknowledged that although challenging, insights gained from studying the towers aided progress in examining 7 WTC.[8]
NIST published its final report on 7 World Trade Center’s collapse in November 2008,[9] following an August draft and public commentary period.[4] A peer-reviewed summary appeared in the Journal of Structural Engineering in early 2012.[10] To simulate collapse initiation and progression, NIST utilized Ansys and LS-DYNA computational models.[11]
The investigation concluded that diesel fuel and structural damage from Twin Towers played a minimal role; instead, uncontrolled fires fueled by office contents burned for seven hours due to lack of water supply. Thermal expansion displaced a critical girder near column 79, causing floor failures between floors eight and fourteen. The loss of lateral support led column 79 to buckle, initiating an east-to-west core collapse that overloaded perimeter columns between floors seven and seventeen, resulting in total building failure. This event marked old 7 WTC as the first known steel high-rise to succumb solely to fire; similar collapses have since occurred at buildings like Edifício Wilton Paes de Almeida, Plasco Building, and Windsor Tower.[9][12]
Many federal investigation files stored within 7 WTC were lost; for instance, the Equal Employment Opportunity Commission reported over ten thousand affected cases.[13] The Secret Service’s largest field office lost vital case evidence,[14] while copies of emails related to the WorldCom scandal held by Salomon Brothers (a Citigroup subsidiary) were destroyed,[15] impacting ongoing regulatory inquiries.
NIST found no support for controlled demolition claims. No explosive sounds or window damage consistent with blasts were detected.[9] The hypothesis that incendiaries such as thermite were used was deemed improbable given observed fire behavior and structural response.[4] Reiterating earlier recommendations from its Twin Towers study,[9] NIST emphasized assessing fire resistance assuming sprinkler system failure,[9] along with considering thermal expansion effects on floor supports.[9] Acknowledging that building codes prioritize occupant safety rather than structural preservation during fires,[9] NIST underscored that structures should not collapse solely due to fire even without sprinkler activation.[9]
Aftermath
The destruction of 7 WTC caused irreparable contamination to Fiterman Hall at 30 West Broadway, part of the nearby Borough of Manhattan Community College. Plans were subsequently updated to demolish the building in 2009 and finalize a new Fiterman Hall by 2012, with an estimated budget of $325 million. Additionally, the eastern exterior of the Barclay–Vesey Building, an iconic Art Deco structure located to the west, sustained damage and underwent restoration costing $1.4 billion. Reconstruction of the new 7 World Trade Center commenced in 2002, leading to its reopening in 2006.
See also
External links
- 7 World Trade Center at SilversteinProperties.com
- 7 World Trade Center on CTBUH Skyscraper Center
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