Police were called to the hotel, 200 block of E. 3rd St., shortly after 10 p.m. Sunday.
The woman, whose name has not been released, was unresponsive and was pronounced dead by medical personnel at the scene. She was an employee of the Blackhawk Bowl and Martini Lounge, which is managed separately from the hotel.
"The Iowa Division of Labor is aware of the fatality," said Molly Elder, spokesperson. She said officials are gathering information to determine whether to open an inspection.
Preliminary information indicated the death was accidental, with no criminal indications, police said.