In the summer of 1950 fear gripped the residents of Wytheville, Virginia. Movie theaters shut down, baseball games were cancelled, and panicky parents kept their children indoors -- anything to keep them safe from an invisible invader. Outsiders sped through town with their windows rolled up and bandanas covering their faces. That year alone, more than 33,000 Americans fell victim -- half of them under the age of ten. Teach your students with this guide from American Experience: "The Polio Crusade."