Before the story, a practical note: I've assembled the ready-made list of every ingredient you'll need to try this one at home. Onto the tale.
The Manhattan is one of the most celebrated stories in cocktail history, usually traced to the Manhattan Club in New York around 1874. Legend says the drink was invented for a banquet honoring Samuel J. Tilden and was hosted by Jennie Jerome, the American socialite who would later become the mother of Winston Churchill. The story is beautiful but historically unprovable, as Lady Randolph Churchill was in England at the time.
What is certain is that the Manhattan was the first cocktail to use vermouth paired with a base spirit, laying the template for the entire family of whiskey-vermouth drinks, including the Martinez, the Rob Roy, and ultimately the Dry Martini itself. It remains the patriarch of all modern stirred cocktails.
The best way to honor these historical cocktails is to serve them with the right attention. A complete barman kit on Amazon is the fastest way to get started and make a good impression from day one. And if you want to go deeper and give your house the proper bar vibe, a professional cocktail bar station is the final, definitive touch.