This was the house drink of the famous 21 Club in New York City during its heyday, back when it was usually called Jack and Charlies's. Jack Kriendler and Charles E. Berns, cousins of Austrian descent, grew up in New York City. In the depths of Prohibition, they decided to go into the speakeasy business. In 1922 they opened their first speak in Greenwich Village, in the unseemly shadow and unpleasant roar of the Sixth Avenue elevated subway; in 1925 they moved across the street to a Spanish-themed speakeasy called Frenton. They were evicted that same year, when the city was condemning buildings to make way for a new underground subway to replace the el. So they moved uptown, to be among all the other fabulous nightspots, and opened their new space at 42 West Forty-ninth Street. It was there, finally, that Jack and Charlie's graduated to a more grown-up crowd, ushered in by Yale graduate Ben Quinn, who brought in other Yalies, including a good smattering of writers. Soon Jack and Charlie's was the favorite of Robert Benchley and Alexander Woollcott, of Dorothy Parker and Edna Ferber.

In 1929, Jack and Charlie were evicted once again, this time to make room for Rockefeller Center, and so they moved into a new space at 21 West Fifty-second Street, where Jimmie Coslove manned the peephole (he was called "Jimmy of the front door") and were they built an elaborate electrified system of secret doors and passageways to hide the liquor in case of a raid. After Repeal, the roving establishment that had been popularly known as Jack and Charlie's finnaly started using a permanent name. During the Great Experiment, they'd changed the name of the businesses regularly to help avoid successful prosecution (the changing names were evidence against a continuity of business). After a brief hiccup in early 1930s, 21, as it was now known, flourished for decades, becoming one of the longest-running success stories in New York.

The Southside was 21's long-running house drink. A Southside is, for all intents and purposes, a mojito made with gin (a strong ingredient, a sour, a sweet, plus mint and soda). And it's up for grabs which came first, the Mojito or the Southside, though it's fairly certain that both were preceded by the third in the triumvirate of minty drinks, the julep, which was being made as long ago as the eighteenth century.[1]

Mint 8 leafs

Gin 2 oz

Fresh squeezed lime juice 1 oz

Sugar syrup 1 oz

This is the best drink to show to a non gin drinker, in order to initiate them to this vibrant potion. For me good gin is a thing of beauty and craftsmanship and I know it takes a lot of effort to reach all those stunning flavors that you get when you sip it. To me the bottle of gin is a cocktail on itself (just add ice). 

When I sip the Southside it reminds me of Wrigley's double mint, with a sour note and some extra herbs on the background, but what I like the most is that minty chewing gum flavor which I loved so much as a child, when I was chewing a pack at once! It's so comforting to find flavors that seemed lost in time and with a little kick added to them.

Now we should all take a seat and watch how the Kevin Diedrich of Liquor.com is kicking the cocktail up one level, with his expert execution.

References: 1. Dale DeGroff - The Essential Cocktail