1956: The Wizard of Oz Shown For The First Time On TV

Source: (IMDb).
Before 1955, most major Hollywood studios did not broadcast feature films on network television, with the exception of Walt Disney. By 1956, this had begun to change, with the studios selling the films to local television stations. On November 3, 1956, The Wizard of Oz became the first major film to be shown in its entirety during a single evening on an entire television network.