Fun Fact: A good Gin is dry, meaning that it lacks a sweet taste.
Jenever is the original Dutch style of Gin, which was distilled in a pot still from a malted grain mash (similar to that used for whisky) to an ethanol content of 50%. Since the distilling techniques were not well refined, the liquid was unpalatable thus herbs were added to mask the flavor. Jenever is still popular today in the Netherlands and Belgium.
Gin, as we know it, evolved from this Dutch Jenever. Gin was developed during the 17th century in the Netherlands, and was intended as a medication. It was sold to treat medical problems such as kidney ailments, lower back pain, stomach ailments, gallstones, and the gout. Gin soon made its way to England through various state conflicts.
When the Dutch Protestant William of Orange and his English wife Mary became co-rulers of England after the "Glorious Revolution" drove James II from the throne, he moved to discourage the importation of brandy from the Catholic winemaking countries by setting high tariffs. As a replacement, he promoted the production of grain spirits by abolishing taxes and licensing fees for the manufacture of local products, such as Gin. This created a market for poor-quality grain that was unfit for brewing beer, and thousands of Gin-shops started production. All this led to very inexpensive, widely available Gin. By the 1720s, it was estimated that a quarter of the households in London were used for the production or sale of Gin. Mass drunkenness became a serious problem, as depicted in William Hogarth's Gin Lane.
(William Hogarth's Gin Lane, 18th Century England)
Gin & Tonic & the British East India Company: In tropical British colonies, quinine was taken as a protection against malaria. The quinine was dissolved in carbonated water to form a tonic water that was extremely bitter. Gin was used to mask the bitter flavor of quinine.
Gin grew in popularity in the US with the advent of Prohibition in 1920. Whiskies were dominant at the time, but required some aging in oak casks, and bootleggers were not in a position to store and age illegal whiskey. Gin, however, did not require any aging, and was relatively easy to make by mixing raw alcohol with juniper berry extract and other flavorings and spices in a large container, such as a bathtub. These Gins were generally of poor quality and taste, a fact that gave rise to the popularity of cocktails in which the mixers served to disguise the taste of the base Gin. Repeal of Prohibition at the end of 1933 ended the production of bootleg Gin, but Gin remained a part of the American culture. Gin was the dominant white spirit in the US until the rise of Vodka in the 1960s.
The Martini: A cocktail made with Gin and dry white Vermouth, shaken with ice, and garnished with an olive. The ratio of Gin to vermouth started out at about 2 to 1, and it has been getting drier ever since. Ernest Hemingway liked to order a "Montgomery,” which was a martini mixed at a 15:1 gin-to-vermouth ratio (these supposedly being the odds Field Marshal Montgomery wanted to have before going into battle). Lyndon Johnson favored the "in-and-out martini,” in which the glass is poured with vermouth, emptied, and then filled with gin. Winston Churchill chose to forgo vermouth completely, saying that the perfect martini involved pouring a glass full of cold gin and looking at a bottle of vermouth. While General Patton suggested simply pointing the gin bottle in the general direction of Italy.
(Thanks to Wikipedia and Tastings.com)