After the United States Supreme Court struck down the federal ban on wagering outside Nevada, states quickly began to legalize and regulate sports wagering. So far, there are 11 states with legal sports betting industries, with more on the way. Tennessee, Montana, Indiana, Illinois, North Carolina, and New Hampshire all legalized wagering in 2019. Here is the current status in some states that have taken action:

New Jersey
Timeline for sports wagering: Legal as of June 2018.
Is betting online legal? Yes
Is betting offline legal? Yes
New Jersey is the reason why sports betting is spreading in the US. New Jersey won a US Supreme Court case which struck down the federal ban. Wagering is legal at its racetracks and in Atlantic City casinos, along with various mobile and online platforms.
Pennsylvania
Timeline for sports wagering: Legal as of November 2018
Is betting online legal? Yes
Is betting offline legal? Yes
Pennsylvania provides a number of sportsbooks in Pittsburgh and Philadelphia, with more opening proximately. SugarHouse is the first online sports betting app to launch in Pennsylvania as of May 2019.
Nevada
Timeline for sports wagering: It’s been legal in the state for decades.
Is betting online legal? Yes, but only via mobile devices.
Is betting offline legal? Yes, there are sportsbooks across the state.
Nevada sports wagering is the grandfather of them all. Casinos around Nevada and Las Vegas already take bets at physical sportsbooks. And most casinos also offer a mobile app that allows you to wager anywhere in the state.
If you want to bet while enjoying other things Las Vegas can offer, the Strip is the place for you. Huge sportsbooks can be found across the city during major sporting events.
Iowa
Timeline for sports wagering: Legal as of August 2019
Is betting online legal? Yes, but with in-person signup at the beginning
Is betting offline legal? Yes.
The state legalized betting and started both retail and mobile sports wagering in August 2019.