It won’t take a billion guesses.

The manager of the Illinois gas station that sold Wednesday night’s $1.04 billion winning Powerball lottery ticket is confident he’ll soon work out who the lucky winner is, even though they could try to remain secret.

“I’d say probably 15% of our customers are traveling through town. The majority of our customers are regulars,” John Marshall, 47, manager of Hy-Vee Gas Fresh & Fast convenience store in Quincy, IL, told The Post Thursday.

“We kind of know our regular customers, and I’ve seen the majority of them so far this morning,” he added, saying that the process of ruling out winners is “like a murder mystery.”

“I sold tickets to some guys passing through this week, one was a maintenance worker working on my coffee machine. I haven’t heard from him yet,” Marshall said, saying he doesn’t know “if he was from Illinois or if he was from Kansas City.”

Marshall’s store gets a $500,000 cash bonus for selling Wednesday’s winner, the second-largest lottery prize ever won in Illinois and the eighth-largest jackpot in the game’s history. The winning numbers were 4, 26, 66, 67, 69, and Powerball 9.

Marshall described the “great buzz” in Quincy, a small city of roughly 40,000 people on the Mississippi River, roughly 137 miles from St. Louis, following the huge win.

“Everyone who’s come in today is happy. Not super happy because they didn’t win, but they’re just happy to have the community on the map,” he said.

“Our regulars are like, ‘Oh, that’s my store,’ and they’re all excited,” he said.

Marshall described Quincy as a “nice, quiet river town,” complete with the famed Midwestern friendliness.

“It kind of makes you feel you’ve traveled back in time because there are people that care. If there’s a neighbor in need, they’re always up to help them. There’s still a lot of caring people in Quincy. It’s a great community,” he said.

“I always tell my customers, ‘Get this lottery ticket and put Quincy on the map.’ And it happened!”

Under Illinois law, the winner has the right to remain anonymous, provided they file a request to keep their identity under wraps, but they must claim the prize within a year of the draw.

Marshall hopes he will get to meet the winner one day.

“I’d like to shake their hand at least if I could,” he said. “I don’t know if I can go when they collect their winnings in Springfield… I wonder if they would invite me. That’d be nice if I could go up there and meet the person at that time too.”

For selling the winning ticket, Marshall’s gas station is set to receive a $500,000 cash bonus, with Illinois lottery officials making the drive from their headquarters in Springfield to visit the Quincy store.

But in typical understated Midwestern fashion, Marshall doesn’t plan on doing anything crazy with the bonus.

“I’d always like to put it towards my house,” he said. “You’d like to pay off your mortgage and then, if there’s any extra, do some investing; you’ve got to do it smart. Maybe you buy something nice, but for the most part, you’ve got to get rid of your debt.”

Since the jackpot run began on May 4, players in the Lincoln State bought more than $53.8 million in Powerball tickets, generating over $21.5 million for the Common School Fund, which supports public education in Illinois.

“This is an exciting day for Illinois,” said Harold Mays, Director of the Illinois Lottery, in a statement. “We’re thrilled for the winner and the retailer that sold the winning ticket.

“Beyond celebrating this incredible win, every Powerball ticket purchased during this jackpot run also helped generate funding for Illinois public schools, demonstrating how the Lottery continues to benefit communities across the state,” he went on.