The Twin Towers of the original World Trade Center in New York City were built in the late 1960s and early 1970s and stood until the attacks of September 11, 2001.

Key dates (quick facts)

  • Construction on the World Trade Center site began in 1966.
  • The North Tower (1 World Trade Center) was structurally completed in December 1970.
  • The South Tower (2 World Trade Center) was structurally completed in July 1971.
  • The full World Trade Center complex, including the Twin Towers, was officially dedicated/opened on April 4, 1973.
  • Both towers were destroyed in the terrorist attacks on September 11, 2001.

Short timeline

  1. 1966 – Site preparation and construction of the World Trade Center begin.
  1. December 23, 1970 – North Tower “topped out” and largely completed.
  1. July 19, 1971 – South Tower “topped out” and largely completed.
  1. April 4, 1973 – World Trade Center complex (Twin Towers) officially dedicated and opened.
  1. September 11, 2001 – Both towers collapse after hijacked airliners strike them.

Simple Q&A style

  • When were the Twin Towers built?
    Mainly between 1966 and 1971, with finishing and opening events through 1973.
  • When were they officially opened?
    At a dedication ceremony on April 4, 1973.
  • When did they fall?
    On September 11, 2001, during coordinated terrorist attacks.

TL;DR: They were constructed from the mid‑1960s to early 1970s, officially opened in 1973, and destroyed on September 11, 2001.

Information gathered from public forums or data available on the internet and portrayed here.