The Glen Island Casino dining hall rose on the foundation of [Starin's Grand Island] Grand Cafe, one of the few structures remaining from Starin's park. The building opened into a series of balconies overlooking the Long Island Sound, which made it an attractive dining and entertaining location.
At the time, the term "casino" was not associated with legalized gambling but instead described "a public social place for entertainment." However, the nightspot was soon living up to the contemporary definition of its name. By 1930, when Prohibition was marking its 10th year in the United States, Glen Island Casino was acquiring a reputation as a speakeasy.
At the same time, the casino had also begun to book up-and-coming musicians for weekend dances. One of the first was Oswald George Nelson, better known as "Ozzie", who set the pace packing the 60-foot by 124-foot hall with throngs of young dancers. Accompanied by his wife, Harriet Hilliard, the Ozzie Nelson Orchestra gained national attention when it played the casino's 1932 season.