Penn National was almost out of the running in Massachusetts, where a 2011 law allowed one slots parlor and up to three resort casinos.
Last month, Tewksbury, Mass., rejected Penn National's bid. Earlier, Penn National tried to negotiate an agreement with Springfield, but MGM Resorts International prevailed.
The Plainville slots plan calls for a $200 million investment by Penn National, which operates 28 casinos and racetracks in the United States and Canada.
Tuesday's vote came amid a frenzy of casino development in the Northeast, even as states have been reporting declines in casino revenue.
As one of the nation's largest casino operators, Penn National is juggling numerous approved projects and proposals.
The Wyomissing company is spending $515 million to build two casinos at Ohio racetracks.
It has proposed a $700 million casino at Rosecroft Raceway in Prince George's County, Md.
In Western Pennsylvania, Penn National has agreed to invest in and manage a proposed $225 million casino and racetrack in Lawrence County. That project's financial backers include Philadelphia-area businessmen Manuel Stamatakis, Peter DePaul, and Ed Snider.
Penn National's proposed South Philadelphia Hollywood casino has a $480 million price tag.
"I hope they aren't distracted," said Joseph Fernandes, Plainville's town administrator.
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