The postwar drive-in theater boom was vital to the expanding independent B movie industry. In January 1945, there were 96 drive-ins in the United States; a decade later, there were more than 3,700. Unpretentious pictures with simple, familiar plots and reliable shock effects were ideally suited for auto-based film viewing, with all its attendant distractions. The phenomenon of the drive-in movie became one of the defining symbols of American popular culture in the 1950s. At the same time, many local television stations began showing B genre films in late-night slots, popularizing the notion of the midnight movie.