The third worst hotel fire in the US was THIS VEGAS CASINO/HOTEL, which caught fire on November 21, 1980 (the same day as Dallas' "Who Shot JR?" episode). 85 people died mostly from smoke inhalation. The casino (which has since changed names and moved down the Strip to a new location) did not have sprinklers since, as a casino, it was occupied 24 hours a day. That soon changed.
MGM Grand [accept Bally's since that is the current name]