1900s - Eastman Kodak Co. founder George Eastman, left, and Thomas Edison pose with their inventions in a photograph taken in the late 1920s. Eastman invented roll film and the camera box, while Edison invented motion picture equipment. By 1930, sound recordings and motion pictures are important resources in many U.S. classrooms. In an article published in 1930, "Educating the Twentieth-Century Youth," a teacher argues that young people should be taught using such 20th-century technology as the radio and the motion picture. (© AP Images)