See 12 Amazing Photos of the World Trade Center Under Construction

  • An elevated view of the construction site for the World Trade Center, New York City, circa 1966.
    Hulton Archive—Getty Images
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  • The pouring of first concrete for the World Trade Center in New York City is shown in September 1966.
    AP Photo
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  • Construction at World Trade Center in New York City on April 16, 1968.
    Robert Kradin—AP Photo
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  • Steelworkers guide a 34-ton steel grillage—the first of 28 that will support the North Tower's core columns—into place 70 feet below street level at the site of the World Trade Center in New York, Aug. 6, 1968.
    Anthony Camerano—AP Photo
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  • Kangaroo cranes in position at the excavation site for the World Trade Center in New York, Dec. 13, 1968.
    Fox Photos—Getty Images
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  • View of the World Trade Center under construction, with a sign announcing the completion schedule, circa 1969, New York City,
    Hulton Archive—Getty Images
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  • The new World Trade Center is shown under construction in New York City, August 1969.
    AP Photo
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  • Aerial view of World Trade Center during construction, August 14, 1969.
    Gordon Rynders—NY Daily News Archive via Getty Images
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  • World Trade Center from the construction site in New York City on Oct. 20, 1970.
    Jim Wells—AP Photo
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  • Workers add a new section to the top of the World Trade Center Building in New York, Oct. 23, 1970, making its height some 1,254 feet, four feet taller than the Empire State Building.
    AFP—Getty Images
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  • Construction of one of the twin towers at the World Trade Center in lower Manhattan, New York City, on Oct. 20, 1970. In the background at right is the Empire State Building with its antenna.
    Jim Wells—AP Photo
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  • A 36-foot long, 4-ton column is hoisted atop the new world's tallest building, the World Trade Center, still under construction in New York City, Dec. 23, 1970.
    Anthony Camerano—AP Photo
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By Lily Rothman

When planning began on the World Trade Center towers, they were only supposed to be 100 ft. taller than the 1,250-ft. Empire State Building, which was still the world’s tallest at that point. But on Dec. 23, 1970—45 years ago—when the North Tower finally “topped out” at its highest height, it had gained even a few more feet on that estimate, reaching 1,368 ft. by the Port Authority’s count.

But the noteworthy nature of the towers wasn’t just a matter of friendly competition among city landmarks. These construction photos make clear that they were a feat of engineering. Viewed in hindsight, of course, it is not just impressive but also bittersweet to see the birth of a building that would meet such a tragic end.

Today, the One World Trade Center tower measures 1,776 ft.

Read original coverage of the plan to build the World Trade Center, here in the TIME Vault: Onward & Upward

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Write to Lily Rothman at lily.rothman@time.com.

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