During the early 20th century in the US, gambling was outlawed by state legislation. However, in 1931, gambling was legalized throughout the state of Nevada, where the US's first legalized casinos were set up.
1931 - Commercial gaming was legalized in Nevada. It was referred to as the "Wide Open Gambling Bill." 1935- Harold's Club opened in Reno (some sources suggest 1936 or 1937).