<P> On July 3 , 1930 , President Herbert Hoover signed the appropriation bill for the Boulder Dam . The dam was later renamed the Hoover Dam during the Truman administration . Work started on the dam in 1931 and Las Vegas ' population swelled from around 5,000 citizens to 25,000 , with most of the newcomers looking for a job building the dam . However , the demographic of the work force consisting of males from across the country with no attachment to the area created a market for large scale entertainment . A combination of local Las Vegas business owners , and Mafia crime lords helped develop the casinos and showgirl theaters to entertain the largely male dam construction workers . </P>
who owned the first casino in las vegas
local Las Vegas business owners Mafia crime lords