 In 1959, Lawrence Wien, owner of New York City's Plaza Hotel purchased the hotel, but signed a management deal for Clark to remain as manager. In the early 1960s, the mafia-financed casino hotels of the Las Vegas Strip and Nevada came under close scrutiny by the FBI, and they placed increased pressure on the Nevada Gaming Control Board to force the mobsters out of Las Vegas. After Sam Giancana was spotted on the premises of Frank Sinatra's Cal Neva Lodge & Casino at Lake Tahoe, his gambling license was removed by the Board and he was forced to sell up and forfeit his share in the Sands Hotel and Casino. The Desert Inn faced similar scrutiny by the FBI, attracting controversy at the same time for the involvement of Dalitz and his mobster associates, but simultaneously called for the prosecution of the FBI for illegal wiretapping. In 1964, Clark sold his remaining share in the hotel to Dalitz and business associates Morris Kleinman, Thomas McGinty and Sam Tucker. He died of a heart attack the following year. The bell captain of the Desert Inn, Jack Butler, remembered Clark: "Wilbur was the greatest guy. Without him this town never would 've got off the ground. Everyone came into the club just to see him and he was all over the postcards. He was the only boss who would agree to have his picture taken".
