Gloria C. Mackenzie of Zephyrhills said in a statement she bought the winning Quick Pick ticket after another ticket purchaser let her cut the line, The Palm Beach Post post reported.
The winner had been a mystery since the May 18 drawing.
WTVT, Tampa, reported Mackenzie didn't attend the news conference announcing her good fortune but she was in the building taking care of the paperwork necessary before she could collect her lump-sum award of about $370.9 million before taxes.
Reporters converged on Mackenzie as she left the building but kept her thoughts to herself, and left with family members in a silver Ford, WTVT said.
Officials said she is the largest sole lottery jackpot winner in U.S. history.
"We bought the winning ticket as a single ticket, even though we bought four other tickets before the drawing," ABC News reported Mackenzie said in a statement read by lottery officials. "While in line at Publix another lottery player was kind enough to let me go ahead of them in line to purchase the winning Quick Pick ticket.
"We are grateful for this blessing of winning the Florida jackpot. ... We hope that everyone will give us an opportunity to maintain our privacy for our family's benefit."
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