Historical epidemic. An outbreak or epidemic of pneumonia that occurred among american legion attendees. This was at a congress in philadelphia, pa in 1976. The bacterium was then named legionella pneumophila.
American Legion. During the bicentennial in 1976, american legion members held a convention in philadelphia. Many of them became ill and some died from a previously unknown infectious agent. The culprit in legionaires' disease was a "new" germ, later named, in honor of the legionaires, "legionella pneumophila.".
A convention. The first significant outbreak happened at a hotel where the american legion was having a conference. A number of legionnaires were affected.
Additional info.... The bacteria, although identified prior to the 1976 american legion conference, was becoming a more prevalent as a disease causing bacteria. In 1976, the outbreak was traced to the bacteria living in the air conditioning/ventilation system of the conference hall. Inhaling water mist infected with the bacteria is one means of infection.