While the Shamrock Shake made its official debut back in 1970, it was actually dreamt up in 1967 by a Connecticut McDonald's owner and operator Hal Rosen, who created the green shake to celebrate St. Patrick's Day. The shake debuted on McDonald's menus three years later.
Those fans who look back fondly on the shake might remember that the frozen dessert wasn't always a minty green delight. Surprisingly, in its first iteration, the Shamrock Shake was more citrusy in flavor. Back then the Shamrock Shake customers sipped down on was a vanilla ice cream mashup with lemon/lime sherbet and vanilla syrup. ZERO mint.
Three years after that shake was introduced, McDonald's did away with the sherbet altogether and sold it as a simple vanilla shake with green food coloring.
In 1983, a significant milkshake moment occurred in fast-food history (OK, we're getting silly here) when McDonald's officially added mint flavor to the recipe, forever solidifying the Shamrock Shake as a one-of-a-kind — albeit fleeting — addition to the menu. Why did McD's wait more than a decade before deciding to shake things up with this minty flavor? The world may never know.
Minty or not, from the moment of its arrival, the Shamrock Shake proved to be a massive hit. Sales from the 1974 shake even paid for Philadelphia's very first Ronald McDonald House.