Caesars
The Caesars Sportsbook can boast its Vegas retail pedigree, and has one of the more extensive online sports betting presences in the US. The parent company bought British bookmaker William Hill in April 2021.
FanDuel
FanDuel also began as a fantasy sports competition operator. In 2018 it was acquired by Irish bookmaker Paddy Power Betfair, and within days opened its first retail sports betting outlet at New Jersey's Meadowlands Racetrack.
DraftKings
DraftKings started life as a daily fantasy sports (DFS) operator, launching DraftKings Sportsbook in New Jersey on August 1, 2018 - making it the first company to offer legal, online, mobile sports betting services. DraftKings also offers retail sports betting in partnership with casinos throughout the US.