Mayor Michael Bloomberg said after two days of struggling to keep the lights on using oil-fueled backup generators since the storm surge of Hurricane Sandy flooded lower Manhattan, the hospital discovered the generators would not be adequate and an evacuation of patients was necessary, the New York Daily News reported.
"We are in the process of finding beds to move these patients to now," Bloomberg said at a briefing.
A string of ambulances waited outside the hospital to ferry patients on gurneys being evacuated with the assistance of the National Guard.
Bellevue, which began operation in 1736, is located near the East River and the hurricane's storm surge sent 17 million gallons of water into the basement.
Members of the National Guard carried the fuel to the roof, where the tanks are located, but once workers got into the flooded basement to look at the generators, they said the damage was worse than expected and the decision to evacuate was made.
In addition, about 20 other healthcare facilities have been evacuated from New York -- 17 nursing homes, NYU Downtown, the Manhattan VA Hospital and the Coney Island Hospital.
Bellevue has been the site of many milestones in the history of medicine and its emergency department was named the city's No. 1 hospital for Emergency Care by New York Magazine.