More than 20 years after her death, Jackie Kennedy, like Audrey Hepburn, maintains her status as a style icon, firmly cemented in the history books. Now, we’re getting a behind-the-scenes peek at the former First Lady‘s sartorial secrets thanks to a memoir written by her longtime assistant, Kathy McKeon.

“The bedroom walk-in closet was jam-packed with Madam’s everyday clothing, all arranged according to color,” McKeon writes in her book, Jackie’s Girl: My Life With the Kennedy Family ($17). “I had never seen such a dazzling selection of shoes! London-look boots, pumps in every color, spotless sneakers for morning jogs around the reservoir.”

The author went on to reveal one little-known fact about all those shoes, giving away the late First Lady’s footwear secret. According to McKeon, all of Kennedy’s footwear had exactly a quarter-inch lift on just one heel, designed with a very specific purpose. “More intriguing to me was the quarter-inch lift affixed to one heel on each pair of shoes, apparently meant to compensate for one leg being slightly shorter than the other,” she wrote. “No one would have ever guessed.”

Huh… who knew? For more little known facts about Jackie O, sure to preorder your copy of the book (now available for pre-order), which drops May 9.

Who else is excited to read this? Tweet us @BritandCo.

(h/t Refinery 29; photo via Ted West, Express Newspapers/Getty)