“The one thing I do not want to be called is first lady. It sounds like a saddle horse,” Jackie Kennedy once famously said.

To be sure, the equine analogy came naturally to the regal young wife of the 35th president, who had been an accomplished rider since her childhood days competing in shows on the East End. Through Oct. 8, rare images of Jackie during her formative years on horseback and engaging in other pursuits and social functions of the smart set can be seen in “Young Jackie on the South Fork,” at the Clinton Academy Museum, blocks away from Lasata, once the Bouvier family’s summer residence in East Hampton.

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The 30-plus black-and-white photographs provide a compelling glimpse of a fresh-faced Jackie before she became Jackie the icon with her stylish pillbox hat and white gloves. Glimmers of her courage, grace and vulnerability are clearly visible in the candid shots taken between the ages of 5 and 15 by Bert Morgan, the dean of high-society photographers, whose subjects ranged from the Duke and Duchess of Windsor to the Rockefellers. The early photos of the girl who would be dubbed “the most photographed woman in the world” by Cecil Beaton were culled from more than 500,000 negatives purchased from Morgan’s estate in 2009 by Shelter Island-based film and video archivist Patrick Montgomery.

In one image, 6-year-old Jackie strikes a pose with her Great Dane, King Phar, at a Long Island Kennel Club dog show, where she’s sporting a double-breasted coat, Peter Pan collar and, most charmingly, a Band Aid-covered skinned knee. Looking askance, her shyness is evident. “She didn’t necessarily want to be photographed, but her socialite mother, Janet Bouvier, encouraged it,” says Jill Malusky, the show’s curator and executive director of the East Hampton Historical Society.

A somewhat older, self-possessed Jackie appears in other photos, wearing a plaid jacket and braids astride her chestnut mare Danseuse or as a guest at a local wedding. “Looking at these images, you know what she is going to be, but she doesn’t,” Malusky notes. “You can see her growing more comfortable in front of the camera.”

A newspaper reporter-style camera similar to the one Morgan used, as well as other accessories including a young girl’s riding habit, are interspersed throughout the photographs.

Arguably the show’s most intriguing picture is one of Jackie perched on a trunk between performances, flashing an impish grin. “We are so used to seeing Jackie so much more buttoned-up, more composed and reserved. It is images like this,” Malusky says, “that humanize her.”