Franklin, Idaho • At “the Home of the Utah Lottery,” La Tienda convenience store in this Idaho border town, three cashiers served a steady and slowly growing stream of customers.

“This is going on our 12th day — our staff is exhausted,” said Shelly Spackman, whose family owns the Kelly’s convenience stores, including La Tienda, regularly the biggest seller of Idaho Lottery tickets in the Gem State.

The onslaught of lottery buyers happened because the two lotteries in which Idaho and 43 other states take part have amassed huge jackpots. The Mega Millions, which drew Tuesday night, boasted a top prize of $1.6 billion. The numbers were: 5-28-62-65-70 with a Mega Ball number of 5. Officials have not yet announced any winners.

The jackpot for the PowerBall lottery, which draws Wednesday night, is up to $620 million.

And the bulk of the business at La Tienda, Spackman said, comes from Utah, one of only two states in the nation (the other is Hawaii) that have no form of legal gambling.

The sign inside La Tienda boasts the store is “Home of the Utah Lottery,” and Spackman said the sign is a favorite for people taking selfies. A scan through the store’s parking lot Tuesday backed that boast, with Utah license plates outnumbering Idaho plates by a 2-to-1 margin.

At 10 a.m. Tuesday, the line was manageable, stretching only to the soda racks at the back of the store. By noon, the line was doubling back to the entrance.

Susan Sellers, a Hyde Park resident who works at a Walmart in the Cache Valley, crossed the state line for lottery tickets — something she said she’s done two or three times recently “since nobody’s been winning.”

If she had won the Mega Millions prize Tuesday, Sellers said, she would have moved back home to Texas, but first “I would help all my friends with medical bills that have cancer,” she said.

Two friends from Logan, Amy Dunn and Dezirae Jones, talked in line about what they might do with a few million bucks. Dunn, a self-employed artist, would have paid for her son’s college and helped out her parents, “and after that, maybe travel.” Jones, a nurse’s assistant, is studying to be a nurse and would have used any lottery winnings to pay her college costs.

“You know, it’s just fun,” said Dunn, who goes north once a year to buy tickets. “You never know; someone has to win.”

Spackman said that cheery attitude usually permeates the line. “Early in the week, everybody’s friendly,” she said. The only sour notes, she said, are from regular ticket buyers who grouse about standing in line with first-timers when the prizes get this big.

The odds of winning are long: 1 in 302,575,350 for the Mega Millions, and 1 in 292,201,338 for the PowerBall. The Mega Millions game was modified in October to allow for more smaller prizes but longer odds for the big jackpot. For comparison, the odds are 1 in 1,171,000 that you’ll be struck by lightning this year, according to the National Weather Service.

If there is a single winner of the big jackpot, that person can choose either $1.6 billion paid out in installments over 30 years — about $53,333,333 a year — or a lump sum of around $904,900,000.

If the winner bought the ticket in Idaho and took the lump sum, he or she would have to pay 24 percent (or just over $217 million) in federal income taxes right off the top, and 6.925 percent (or more than $62 million) to the state of Idaho.

If that winner lived in Utah, the Beehive State would claim another 5 percent, or a bit over $45 million, in income tax. So a Utahn who took the lump sum would still walk away with nearly $580 million after taxes.

At La Tienda, Spackman notices the difference when the lottery prizes get big. On a normal week, she said, lottery tickets account for about a quarter of the store’s business, with the rest taken up by the usual snacks, sodas and La Tienda’s “great big huge” beer room.

“When the lottery is high, it takes over,” Spackman said. “Everybody gets let out of their cage.”