Voters in Massachusetts have upheld the state's expanded gambling law, which will allow land-based casinos to begin operating in the state.
The votes were counted on Tuesday evening, with an approximate 60% choosing to keep the current law in place.
The Massachusetts Expanded Gaming Act was passed in 2011, allowing for three destination resort casinos and one slots facility.
It will now remain in place after the electorate turned down the opportunity to repeal it.
MGM Resorts International, Wynn Resorts and Penn National Gaming had all been eagerly awaiting the result of the vote.
Wynn Resorts can now push ahead with its $1.6bn resort on the Mystic River waterfront in Everett, while MGM plans to spend $800m to develop a casino in Springfield.
Slot machines could be in operation in the state by the summer of 2015, with Penn National Gaming planning a slot parlour in Plainville.
Casino firms financed a multi-million dollar campaign to see the law upheld.
Frank Callahan, president of the Massachusetts Building Trades Council said: “We always thought we were going to win handily. The members have been really working hard. This will mean about 6,500 jobs.”
The Suffolk Downs racetrack in the state has closed after having its joint bid for the sole Boston-area casino licence rejected.