1983–2001

A view of the original 7 World Trade Center from the WTC observation deck, taken on August 14, 1992.
taken from Wikipedia

Transfer trusses used on the 5–7th floors to redistribute load to the foundation
The original 7 World Trade Center was a 47-story building, designed by Emery Roth & Sons, with a red granite façade. The building was 610 feet (186 m) tall, with a trapezoidal footprint that was 330 ft (101 m) long and 140 ft (43 m) wide.[1][2] Tishman Realty & Construction managed construction of the building, which began in 1983.[1] In March 1987, the building opened, to become the seventh structure of the World Trade Center.
The building was constructed above a Con Edison substation, which had been on the site since 1967.[3] The substation had a caisson foundation designed to carry the weight of a future building on the site of 25 stories containing 600,000 sq ft (55,700 m²).[4] The final design for 7 World Trade Center was for a much larger building covering a larger footprint than originally planned when the substation was built.[5]
The structural design of 7 World Trade Center included features to allow a larger building than originally planned to be constructed. A system of gravity column transfer trusses and girders was located between floors 5 and 7 to transfer loads to the smaller foundation.[3] Existing caissons installed in 1967 were used, along with new ones, to accommodate the building. The fifth floor functioned as a structural diaphragm, providing lateral stability and distribution of loads between the new and old caissons. Above the seventh floor, the building's structure was a typical tube-frame design, with columns in the core and on the perimeter, and lateral loads resisted by perimeter moment frames.[4]
A shipping/receiving ramp, which served the entire World Trade Center complex, occupied the eastern quarter of the 7 World Trade Center footprint. The building was open below the third floor, providing space for truck clearance on the shipping ramp.[4] The spray-on fireproofing for structural steel elements was gypsum-based Monokote which had a two-hour fire rating for steel beams, girders and truss, and a three-hour rating for columns.[6]

7 World Trade Center, behind and to the left of the Twin Towers
Mechanical equipment was installed on floors four through seven, including 12 transformers on the fifth floor. Several generators in the building were used by the Office of Emergency Management, Salomon Smith Barney and others.[6] Storage tanks contained 24,000 gallons (91,000 L) of diesel fuel to supply the generators.[7] Fuel oil distribution components were located at ground level, up to the ninth floor.[8] After the World Trade Center bombings of February 26, 1993, New York City mayor Rudy Giuliani decided to situate the emergency command center and associated fuel tanks at 7 World Trade Center, possibly adding to the devastation of the September 11 attacks.[9][10][11][12][13][14] The roof of the building included a small west penthouse and a larger east mechanical penthouse.[3]
Each floor had 47,000 sq ft (4,366 m²) of rentable office space which made the building's floor plans considerably larger than most office buildings in the City.[15] In all, 7 World Trade Center had 1,868,000 sq ft (174,000 m²) of office space.[6] Two pedestrian bridges connected the main World Trade Center complex, across Vesey Street, to the third floor of 7 World Trade Center. The lobby of 7 World Trade Center had three murals by artist Al Held: The Third Circle, Pan North XII, and Vorces VII.[16][17] A sculpture by Alexander Calder, called WTC Stabile (also known by other names, The Cockeyed Propeller and Three Wings) was on a plaza in front of the building.[18]