The betting estimates displayed Monday that Americans are expected to place $10.4 billion bet on March Madness, according to American Gaming Association, a lobbying firm that represents the casino industry. Those who place worth of money spent on the NCAA Tournament is expected to increase 13 percent from last year. In 2016, bettors wagered $9.2 billion.

AGA noted that only approximately $295 million -- or 3 percent -- is placed in the Nevada sportsbooks legally, which makes up the remaining $10.1 billion to be wagered on illegal offshore websites or through local bookmakers.

Nevada is the one of the few states that are allowed to operate sportsbooks. Outside of Nevada, $150 billion is spent on sports betting each year -- illegally.

"The federal ban on sports betting is an utter failure -- depriving states of vital tax revenues and preventing millions of fans from wagering legally on games," AGA president and CEO Geoff Freeman said. "It's time for Washington to get out of the way and enable states to reap the rewards of a regulated sports betting marketplace."

Americans received 70 tournament brackets to fill out and complete. The cost of brackets averaged $29 a piece.

Supporters continue to push sports betting legalization and regulation

As March Madness continues to grow in popularity, Americans gamble on it.

Regardless of whether it is legal or illegal, the NCAA, which oversees athletic programs of U.S. colleges and universities, did not support the notion of gambling on the tournament. The organization senses that betting on NCAA could jeopardize student-athletes' interests and damage the integrity of the games.

The AGA and supporters have spoken out against the Professional and Amateur Sports Protection Act (PASPA), a 1992 federal law that prohibits most states from authorizing sports gambling operations.

The AGA issued demand with federal government to discuss on the regulation and legalization of the sports betting.

The support for the legal sports gambling has been gained from commissioners of professional sports leagues, including Adam Silver of the NBA, Rob Manfred of the MLB, Jay Monahan of the PGA and Don Garber of the MLS.

Silver is a legalization proponent who emboldens Congress to form a federal framework of regulation to enable states to run sports betting operations.

Betting on legendary sporting events

Last March, Nevada held a betting record after wagering $422 million on basketball hoops at the sportsbooks. Winning $21.5 million on basketball by sports books in Nevada last March has become the second-most profitable basketball month in sports betting history. Las Vegas sportsbook directors noted that the cost of betting on NCAA Tournament this year varies from $20 to $50.

According to a report by Nevada Gaming Control Board, people spent a total of $138.4 million on Super Bowl LI, which multiple sports analysts considered the New England Patriots' 34-28 victory over the Atlanta Falcons as one of the greatest comebacks in NFL history. Prior to Super Bowl game, the AGA projected that people would wager $4.7 billion on a football championship game.