7 World Trade Center (1987–2001)

7 World Trade Center (7 WTC, WTC-7, or Tower 7), colloquially known as Building 7, was an office building constructed as part of the original World Trade Center Complex in Lower Manhattan, New York City. The tower was located on a city block bounded by West Broadway, Vesey Street, Washington Street, and Barclay Street on the east, south, west, and north, respectively. It was developed by Larry Silverstein, who held a ground lease for the site from the Port Authority of New York and New Jersey, and designed by Emery Roth & Sons. It was destroyed during the September 11 attacks.

The original 7 World Trade Center was 47 stories tall, clad in red granite masonry, and occupied a trapezoidal footprint. An elevated walkway spanning Vesey Street connected the building to the World Trade Center plaza. The building was situated above a Consolidated Edison power substation, which imposed unique structural design constraints. When the building opened in 1987, Silverstein had difficulties attracting tenants. Salomon Brothers signed a long-term lease in 1988 and became the anchor tenant of 7 WTC.

On September 11, 2001, the structure was substantially damaged by debris when the nearby North Tower of the World Trade Center collapsed. The debris ignited fires on multiple lower floors of the building, which continued to burn uncontrolled throughout the afternoon. The building's internal fire suppression system lacked water pressure to fight the fires. It began to collapse when a critical internal column buckled and triggered cascading failure of nearby columns throughout, which were first visible from the exterior with the crumbling of a rooftop penthouse structure at 5:20:33 pm. This initiated the progressive collapse of the entire building at 5:21:10 pm, according to FEMA,^: 23 while the 2008 NIST study placed the final collapse time at 5:20:52 pm.^{: 19, 21, 50–51} The collapse made the old 7 World Trade Center the first steel skyscraper known to have collapsed primarily due to uncontrolled fires. A new building on the site opened in 2006.