March to Legalization
From 1931 until 1978 the State of Nevada was the only place in the United States that offered legal, real-money casino gaming.
The Silver State’s casino monopoly established Las Vegas as the template for all the casino towns that followed, including Atlantic City in 1978. Once AC opened for business, plenty of states began offering legal gambling of one kind or another (though most started with just a lottery and added casino gaming later.)
Today, gambling is legal – in one form or another – in every state but Utah and Hawaii. This widespread acceptance of land-based gambling opened the door for the current wave of online gambling liberalization.