This is taken directly from Galliano's circa-early 70's promotional recipe booklet entitled "Welcome to Galliano's World of New Tastes" where they promise that "Italy's premier liqueur is also the perfect mixing ingredient."
The Harvey Wallbanger is probably single-handedly responsible for popularizing Galliano, and why you can spot its signature narrow, skinny, spire of a bottle with its golden liqueur in the back row of every bar.
The Harvey Wallbanger is pretty much the quintessential 70's drink. Equally good as an eye-opener or as a drink of choice at one of those singles bars that became so popular in that decade, it proved a reliable stand-by drink order.
Where did the name come from, though? Well, here's one take on the origins of the drink: