It has been a while since I've read it so I don't have a specific answer, but I'd recommend checking out Roll The Bones: The History of Gambling by David Schwartz.

Most of the early established casinos were in places with natural hot springs and baths. These were already vacation destinations for the wealthy so it was a natural place to setup gambling houses as well. Baden Baden in Germany is one example of a Roman bath town that has had institutionalized gambling for most of its history.

Hard to know what you mean by "large scale", but I believe the opening of the Flamingo hotel in Las Vegas in 1946 was when everything started to change. $6 million was spent to build it as a luxury gambling resort which was about 10 times more money than the largest casino previously spent to build (around $425k about 5 or so years earlier). After the Flamingo opened, the El Rancho scrambled to match the sophistication of the Flamingo. The snowball just kept rolling from there.