In 1970, McDonald's introduced a new flavor to its small selection of milkshakes and made it only available around the middle of March, in honor of the holiday where everyone's Irish.
Today, only a select number of Golden Arches franchises offer the Shamrock Shake, the tip of the fast food chain's green bowler to St. Patrick. (During the '80s, the company might have gone a little far with its Irish references, airing some possibly offensive commercials for the milkshake on television. See one below)
Fans devoted to the minty green treat have taken to the Web to share their affection and pinpoint where fellow admirers can get their fix. Tracking it as though it were an expensive craft beer, ShamrockShake.com allows followers of the fickle beverage to find franchises carrying it on tap.
"Just bought 4! No line! (though, it`s also 1030a)" one tipster wrote Wednesday morning to confirm a location in New York City.
Shane Ferguson, of North Vancouver, B.C., Canada, launched the site in 2006. He told CBSNews.com there's nothing he'd change about the shake -- and as of Wednesday afternoon he's already consumed four of them.
"I was curious where they were sold since I was unable to locate a shake for myself," Ferguson said via e-mail. "So I thought, Throw the site up and maybe someone will drop a tip I can use, and voila!"
Ferguson estimated about 300 Shamrock Shake tips have been added to the site this St. Patrick's Day although not all of the site's posts bear good news.
"I've lived in NJ my whole life and lived off of the shamrock shake this time of year," a tipster posted Monday. "Now I'm at school in Austin (Texas) and have yet to find one person who has even heard of it!"