Jonas Salk was an American medical researcher best known for the discovery and development of the first polio vaccine. First recorded in 1835, polio was a medical oddity that baffled researchers for years. As the fear of polio increased each year, funds to combat it increased from $1.8 million to $67 million by 1955. On April 12 of that year news of the vaccine was announced and, within minutes, the news of the event was carried coast to coast by wire services and radio and television newscasts.
As Whistle took place "in the 1950s" (Whistle, 1), one could assume Lewis's ordeal with finding the whistle occurred some time after 1955.