Pennsylvania is now the nation's second biggest gaming market, knocking Atlantic City down to third on the list.

Las Vegas continues to rank at the top of the list. Pennsylvania casinos took in $3.16 billion from slots and table games in 2012, compared to Atlantic City's $3.05 billion. Pennsylvania's first casino opened at the end of 2006 and they were slots-only until the summer of 2010.

Pennsylvania's rapid gaming growth is attributed to the state putting casinos in highly populated cities, such as Philadelphia and its suburbs, however, some Atlantic City casinos will loudly point out that you are comparing an entire state, which includes several large population centers, to one city.