In the wake of the United States' economic downturn and the legalization of gambling in adjacent and nearby states (including Delaware, Maryland, New York, and Pennsylvania), four casino closures took place in 2014: the Atlantic Club on January 13; the Showboat on August 31; the Revel, which was Atlantic City's second-newest casino, on September 2; and Trump Plaza, which originally opened in 1984, and was the poorest performing casino in the city, on September 16.

How many casino closures took place in Atlantic City in 2014?