I feel compelled to add a bit of information to m_turner's fine and informative writeup above. The martini may be the only drink in the world which has received the solemn respect of standardization. The American Standards Association (predecessor to the American National Standards Institute), whose initials live on in photographic film ratings, ceased operations in 1966 before morphing into the aforementioned ANSI. The last published standard from that body was, in point of fact, American Standard K100.1 1966: Safety Code and Requirements for Dry Martinis. This opus was produced by Sectional Committee K100 on Liquids Management, and was approved as a standard in August of 1966.

Thanks to George B. Kaufmann, writing in the journal Chemical Educator in 20011, we have the following excerpt, which defines some of the oft-debated characteristics of the drink:

Dry Martini: A cocktail made with English or American dry gin of at least 86 proof and dry vermouth, preferably French in origin, in accordance with requirements of this American Standard.

Gibson: An unpardonable form of perversion. See Onion Soup.

Lemonade: A term applied to drinks which have been subjected to the peel of a lemon. There is no place for the rind of any citrus fruit, or its oils, in an American Standard dry martini.

Onion Soup: the unholy abomination produced by the introduction of one or more pickled onions into a dry martini cocktail.

Rocks: the solid state of H2O on which an American Standard dry martini is never served.

Vodka: A distilled alcoholic beverage made originally from potatoes, but now encountered in grain alcohol versions. It may be clean, palatable, and nonlethal, and when encountered in this form, is a fitting accompaniment for fresh caviar. It is never employed in a dry martini.

2.1 Basic Nomenclature: The American Standard dry martini shall come in the following three sizes:

  • Regular–not less than 3.5 oz.
  • Large–not less than 5 oz.
  • Double–not less than 7 oz.
3.1 General: Only the following three ingredients shall be used in the preparation of the American Standard dry martini.

3.3.1 Use of Vermouth: The employment of vermouth in an American Standard dry martini shall not be mandatory, provided no other ingredient is employed as a substitute.

3.4 Olives: While the use of olives is not encouraged, nothing in this specification shall be construed to mean that the inclusion of an olive will not be accepted, provided it conforms to Table 1 and subparagraphs 3.4.1 and 3.4.2.

I have been fruitlessly searching for an actual hardcopy of this standard for years and years. I'm told by a couple of engineers who have seen it that the copies they have seen have been enshrined in libraries and trophy cases, so the likelihood of my finding one is low - but we do what we must, because we can.

ATTENTION:

As of October 2010, The long wait is over.

The internet told me that this did not exist. I refused to believe that.

Professional archivists and librarians told me that this did not exist. I refused to believe them.

Finally, after several years of searching, the Internet has come through. A computer museum located a copy in its archives and scanned it in August 2010.

Ladies and Gentlemen, I give you: K.100-1/1966.

Safety Code and Requirements for Dry Martinis.

(A version with darker text can be found here, but that version is missing the second page which states flatly that this is the final American Standard.)

Thanks to the excellent Oaklift, we also have a source for the subsequent revision - K100.1-1974, American National Standard Safety Code & Requirements for Dry Martinis.

The FDR Martini

There have been many famous martini drinkers, but perhaps none so distinguished as President Roosevelt. He famously introduced Stalin to the martini (who, after finishing it, is reputed to have said "Well, all right, but it is cold on the stomach.") and indulged in all-night benders with Winston Churchill at the White House. Churchill was partial to the martini, and his version is said to have been mixed by pouring a glass full of cold gin while looking at a bottle of vermouth. Nikita Khruschchev called the martini "America's most lethal weapon" - high praise indeed.

While FDR's martini may not conform to K100.1 as listed above, it is recognizably a martini:

Rub the lemon twist around the rim of a chilled martini glass. Shake the gin, vermouth and olive brine with cracked ice (or, preferably, in a chilled shaker). Strain into glass; garnish with twist.

The Fissionable Martini

Another American classic, the Fissionable Martini is attributed to J. Robert Oppenheimer and the men of The Manhattan Project.

Additional Trivia

The phrase 'Dry Martini' does not in fact refer to the amount of vermouth in the cocktail. Rather, it indicates that the drink should be constructed with French (dry) vermouth, rather than the Italian (sweet) version with which it originated. This is how FDR's mix, with only a 2:1 ratio of gin to vermouth, can still properly be called a 'dry martini.' However, requesting a martini be made 'dry' as an adjective in most venues will indicate to the bartender to use a smaller amount of vermouth in the mix. At the extreme, there is the aforementioned Churchill Martini or Fissionable Martini - or the Optical Martini described in K100.1/1966, or Noel Coward's version in which one pours a drink of gin and then waves it in the direction of Italy.

Notes:

1 - Kauffman, George B. "The Dry Martini: Chemistry, History, and Assorted Lore." Chemical Educator 2001.6 (2001) 295-305.