For most of U.S. history, sports betting was rare.
Some people certainly bet on sports illegally via a bookie, or placed bets in the few places where it was legal, such as Nevada.
However, gambling policy took a sharp turn in 2018, when the Supreme Court decided that each state in the U.S. had the right to legalize or prohibit sports wagering as they saw fit.
The effects of this ruling were swift, with many states introducing legislation to legalize sports betting within months. Four years later, more than 30 states have legalized sports betting, and many more are working to legalize it in the immediate future.