William LeMessurier

William "Bill" James LeMessurier, Jr. (; June 12, 1926 – June 14, 2007) was a prominent American structural engineer.

Born in Pontiac, Michigan, LeMessurier graduated with an AB from Harvard, went to Harvard Graduate School of Design and then earned a master's degree from Massachusetts Institute of Technology in 1953. He was the founder and chairman of LeMessurier Consultants. He was awarded the AIA Allied Professions Medal in 1968, elected to the National Academy of Engineering in 1978, elected an honorary member of the American Institute of Architects in 1988, and elected an honorary member of the American Society of Civil Engineers (ASCE) in 1989. In 2004, he was elevated to National Honor Member of Chi Epsilon, the national civil engineering honor society.

While responsible for the structural engineering on a large number of prominent buildings, including Boston City Hall, the Federal Reserve Bank of Boston, the Singapore Treasury Building and Dallas Main Center, LeMessurier is perhaps best known for a structural controversy. As the result of the questions of a student (Diane Hartley), LeMessurier re-assessed his calculations on the Citicorp headquarters tower in New York City in 1978, after the building had already been finished, and found that the building was more vulnerable than originally thought (in part due to cost-saving changes made to the original plan by the contractor). This triggered a hurried, clandestine retrofit which was described in a celebrated article in The New Yorker. The article, titled "The Fifty-Nine-Story Crisis," is now used as an ethical case-study.

LeMessurier died in Casco, Maine on June 14, 2007 as a result of complications after surgery he underwent on June 1 after a fall the day before.