09/06/2026
William LeMessurier: The Calculation He Did Not Have to Run
In 1978, a question from a student reached William LeMessurier. He had already answered it.
Diane Hartley, a Princeton undergraduate, was writing her senior thesis on the Citicorp Center, the new skyscraper at Lexington and Fifty-Third in Manhattan.
The tower stood on four massive columns set at the middle of each face, not the corners, to span a church that could not be moved. She wanted to know whether that arrangement handled winds arriving at an angle the same way it handled winds straight on.
She put the question to a junior engineer at LeMessurier's firm, and it was passed up to him.
LeMessurier ran the numbers again.
During construction, his firm had approved a change. The welded connections in the diagonal bracing had been switched to bolted ones. Bolted connections were cheaper. Under quartering winds — winds hitting at forty-five degrees — they were also weaker.
When he put the revised analysis together, the tower could fail. A storm that strong hit New York roughly once every sixteen years.
He was the only person who knew. The building had passed inspection. No regulator was asking questions. LeMessurier had a firm, a career, a reputation he had spent three decades building.
He disclosed the problem to his insurance carrier, to Citicorp, and to city officials. He hired engineers to verify the work.
Starting in August 1978, crews went up at night and welded steel plates over the bolted connections throughout the bracing. The offices stayed occupied during the day. An evacuation plan for the surrounding blocks was ready if a storm arrived before the work was done.
That September, Hurricane Ella moved up the Atlantic coast.
It turned out to sea.
The repairs finished in October. No one died.
LeMessurier's license was not revoked. He was not sued. The engineering community treated the disclosure as a model. He taught at Harvard and lectured openly on the case for the rest of his career.
He died in 2007. The building is still there.
The people who work in it do not know his name.
That's Quiet Valor.
What about you?
Have you ever found a mistake that only you knew about? Tell us what you did in the comments.
Source: The New Yorker, "The Fifty-Nine-Story Crisis," Joe Morgenstern, May 29, 1995 — https://www.newyorker.com/magazine/1995/05/29/the-fifty-nine-story-crisis.
The student's identity: 99% Invisible, "Structural Integrity," April 15, 2014 — https://99percentinvisible.org/episode/structural-integrity/
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When it was built in 1977, Citicorp Center (later renamed Citigroup Center, now called 601 Lexington) was, at 59 stories, the seventh-tallest building in the world. You can pick it out of the New York City skyline by its 45-degree angled top. But it’s the base of the building that really makes the...