Stir orange juice and vodka in highball glass with ice. Float Galliano. (Modern recipes include garnish of orange slice and cherry.)
The original recipe is very simple: 1 : 1/2 : 6 as shown on several versions of the posters. Modern recipes increase the vodka slightly and reduce the orange juice considerably. I typically build it as 1.5 : 1/2 : 4 with the orange juice fresh squeezed from trees in my backyard.
This highball was popularized by a 1969/1970 poster campaign featuring the recipe with a cartoon surfer named Harvey Wallbanger. The ad campaign was courtesy of George Bednar and Bill Young was the artist. Donato Antone claims to have created the cocktail at his Sunset Boulevard bar in 1952--but there is no record of the establishment, and his biographical information indicates he was running a bartending school in Hartford, CT from 1949 on. It has been suggested that Antone/Bednar/Young all had parts in creating the cocktail and/or the backstory.