The Supreme Court is expected to rule soon on whether to allow legalized sports betting across the country, and many states are lining up at the gate to cash in on the possible tax revenue and job creation.

Millions of people regularly wager on college and professional games, from office pools to internet gambling to placing bets with a bookie. About $150 billion in sports bets are placed each year, according to estimates from American Gaming Association President Geoff Freeman.

Under...