"Passing Pennsylvania should be momentous but it is almost certainly going to be short-lived, as the decision to return to in-person registration will likely mean the end of growth for the Illinois sports betting industry," said Jessica Welman, analyst for PlayIllinois.com. "Open registration has been a key component in making Illinois one of the largest sports betting markets in the country. Forcing people to physically appear in a retail sportsbook is a counterproductive measure, which should be apparent whenever Illinois April data is released."

With open registration still in place in February, Illinois retail and online sportsbooks attracted $509.8 million in wagers, according to official data released Friday. That is down 12.3% from the record $581.6 million in January, an expected dip with fewer days during the month and only one NFL game to bet.

Bettors placed $18.2 million per day in the 28 days of February, which was down slightly from $18.8 million per day in January. Illinois' relatively modest pullback made it the third-largest U.S. market in terms of money wagered, gaining ground on leaders New Jersey ($743 million) and Nevada ($554.1 million), while topping Pennsylvania ($509.5 million) for the first time.

February's handle also produced $30.3 million in operator revenue, down 38.7% from the record $49.4 million in January. But the month's win produced $35.4 million in taxable revenue, which yielded $5.3 million in taxes for the state and another $541,832 in local taxes.

"February's results in Illinois actually compare well to the other major markets in the U.S., showing that the state had yet to reach its ceiling," said Joe Boozell, analyst for PlayIllinois.com. "Even with the return of in-person registration, operators have set a good foundation of bettors that will sustain the industry, even as the rules stunt the market's growth."

For the first time in months, retail sportsbooks were open for a full month, attracting $19.6 million in bets. But online betting still drove 96.2%, or $490.2 million, of the state's handle. That is down from 98.9%, or $575.2 million, in online betting in January.

DraftKings/Casino Queen remained the market leader by accepting $199.8 million in online and retail wagers in February, which was down from the operator's $244.2 million handle in January but still represented 39.2% of the state's total handle. $196.5 million of February's bets came online.

FanDuel/Par-A-Dice Casino was second with its $158.9 million handle, $158.4 million of which came online.

"Barstool had just three weeks to build a customer base in an open environment, which should put it at a permanent disadvantage against the market leaders," Welman said. "That said, their brand is popular and should draw significant interest, helping to grow the market. It could be the last hurrah, of sorts, as new operators might be deterred by in-person registration."