What year did McDonald's launch the shamrock shake?

While one creative Connecticut McDonald's owner invented the shamrock shake in 1967, McDonald's didn't share the luck of the Irish with the rest of America until 1970. The original shake wasn't even the minty green masterpiece we know today. It was a vanilla shake mixed with lemon-lime sherbet that kind of looked like a science experiment gone wrong. McD's finally nailed the recipe a few years later when they switched to the simple combo of vanilla ice cream and mint syrup.