Marty O'Brien's was a bar and grill run by Dolly and Marty Sinatra on the corner of Fourth Street and Jefferson, Hoboken. It was named after Marty's boxing persona, which also made good commercial sense as Hoboken had a large Irish population. They also catered for Italian's by serving pasta and sandwiches. it was funded by Dolly's mother.
As their was a prohibition, they needed to get alcohol and they needed protection, which they found in the mob.