Sheelah Ryan, 69, who won $55.2 million in the Florida lottery in 1988, then the nation's largest single jackpot. Miss Ryan quit her job as a real estate agent after winning the Sept. 3, 1988, drawing and established the Ryan Foundation to help build low-cost housing in north-central Florida and pay overdue rents for single mothers. The organization's shelter program also housed women and children and attempted to assist them in getting back into society. Miss Ryan had never been aboard an airplane until after she hit the jackpot, when she flew to Tallahassee to claim it. She continued her low-key lifestyle after becoming an instant millionaire. Her winnings were the nation's largest individual jackpot until July 7, 1993, when Leslie Robins of Fond du Lac, Wis., claimed $111 million in the Powerball Lottery drawing. In Winter Springs, Fla., on Saturday of cancer.