Legionnaires' Disease

Philadelphia, the birthplace of the United States, played host to millions of tourists and hundreds of gatherings as America celebrated its 200th year of independence. History was made that summer of 1976 - not because of the bicentennial, but because of the mysterious death of 34 people at an American Legion convention. The groundbreaking investigation by the CDC had to explain why dozens inside a hotel - and some who just walked by outside - all got sick.