Gambling was sporadically legal and illegal in Nevada prior to 1931. But, even when it was illegal, nobody enforced the law because there were too few residents who cared about gambling, and not enough sheriffs, DAs or governors who thought they could get a ride to higher office by prosecuting gambling operators.

The difference in 1931 was that work was about to start on the Hoover Dam, the state's largest public works project. The Dam brought almost 10,000 workers to a site only ~20 miles from Las Vegas--then the state's fourth largest city with 5,000--count 'em 5,000--residents. The politicians knew the Dam workers were going to gamble their paychecks away in Vegas, so why not legalize gambling and tax the profits. Within the first month, about 200 out-of-state people applied for gaming licenses. Many were involved with OC. They saw that Prohibition would be repealed soon, and were looking to cash in on legalized gambling. Some of them got "respectable" through leganized gambling.