The jackpot, growing since Dec. 17, is expected to spark a frenzy of Powerball ticket sales.
"That will be the largest the jackpot has ever been," Tina Potthoff, spokeswoman for the Iowa Lottery, said Thursday.
Jasmina Goretic, a clerk at a Dahl's Food Mart in Des Moines, Iowa, said the store might have an extra person staff the courtesy counter to handle Powerball sales before Saturday's drawing.
"We expect a crowd," she said. "It's been crazy already."
The Powerball jackpot tops the previous lottery record, which was $363 million for the Big Game — the forerunner of Mega Millions. It was won by two ticket holders in Illinois and Michigan in 2000. However, that Big Game prize actually had a larger cash payout than the current Powerball will boast — $181.5 million compared to $177.3 million.
After no winner was picked in Wednesday's $308.8 million Powerball drawing, the jackpot climbed past the game's previous record of $340 million, which was won by an Oregon family in October.
The game grew out of the Lotto America game, which started in 1987 in seven states. It evolved into Powerball in 1992 and, since then, more states have been added — 28 plus the District of Columbia and the U.S. Virgin Islands. Yearly ticket sales are into the billions of dollars.
The chances of winning the jackpot are 1 in 146.1 million.
The odds don't keep Nancy Chavannes, of Windsor Heights, Iowa, from purchasing a ticket. She plans to get hers on Saturday. She usually only plays when the jackpot gets near a record, but admitted she would be happy with one of the smaller prizes.
"I would take the $100,000, I'm not picky," she said with a smile.
Chavannes said she likes to daydream about what she would do with her winnings, including expanding her travel agency and wine shop in the Des Moines skywalk.
"We buy a Powerball ticket, go home, have a bottle of wine ... and imagine," she said.
By Amy Lorentzen