The prize was shared by two individuals, who agreed to split the prize if won - and they stayed true to their word.
The winners wish to remain anonymous.
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The ticket was purchased at the Speedway #4250 on Touhy Avenue in Des Plaines at the end of July, according to lottery officials.
It was the third largest jackpot in U.S. history.
The winners have spent the past few weeks working with professional legal and financial advisors to support the claim process, and have opted to take the lump sum payment of $780.5 million.
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The Mega Millions jackpot roll started on April 16 until July 29, and the state of Illinois was also a big winner.
During the jackpot roll, the Illinois Lottery generated $34 million for the Common School Fund through the sale of the game.
Retailers earned $3.75 million in payable commission and bonuses for selling winning tickets, and in total there were more than 1.4 million winning tickets in Illinois collecting $11.8 million in prizes (excluding the jackpot), including four individuals who won prizes of $1 million.
"It's definitely the largest jackpot Illinois has seen -- third largest of all time in the U.S," Illinois Lottery Director Harold Mays said.
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