New Legitimacy: Organized crime was soon to have a formidable adversary in its bid to control Las Vegas — corporate cash. Though Las Vegas had developed a powerful local economy, few major outside investments were made in the city, due primarily to mob infiltration and its inherent ties to illegal activities. That would change dramatically with the 1966 arrival of billionaire Howard Hughes. A legitimate businessman, Hughes was nonetheless eccentric and dramatic, a style suited to the Las Vegas ethos. True to the myth, the reclusive Hughes immediately cloistered himself in the Desert Inn's penthouse. Several weeks later he was asked — then ordered — to vacate the room to make room for high rollers, whereupon he promptly bought the property and fired the management. Thus began Hughes' legendary three-year, $300-million Las Vegas buying spree. When it was over, Hughes owned six casinos, an airport, and an airline, along with numerous plots of land stretching from the Strip to the mountains. Hughes' actions would have beneficial repercussions, both immediate and lasting. Because of the new legitimacy Las Vegas acquired from Hughes' investments, established companies such as Hilton Hotels bought into the gaming business, and their influence helped draw a line in the desert sand between legitimate operations and mob casinos, where illegal skimming of profits was rampant. That, combined with the formation of the Nevada Gaming Control Board, would signal the beginning of the end for heavy mob influence in the city. Las Vegas with a Vision As corporations moved in and the mob was slowly pushed out, a new Las Vegas emerged. The legitimization of gambling led to its increased legalization across the US. What was once a sure thing became much more competitive. Casino operators had to reassess the nature of their business. The first to really do so was Steve Wynn, a Las Vegas resident and owner of the Golden Nugget. In the mid-1980s, Wynn began plans to reinvigorate Las Vegas with a new resort. He bought several Strip properties — the Silver Slipper and Castaways among them — and demolished them to make way for a new kind of resort — Mirage —  which became an instant success. 
What signified the ending of heavy mob influence in Las Vegas?
The formation of the Nevada Gaming Control Board