There may be WAY too much information to handle in this fashion, but we may not know unless we try. The timeline should be broken down into individual "Eras". If this list gets too top-heavy, we can split each era into their own page.
The following detail the major milestones in cocktail history.
Pre-Dawn (before 1800)
It was in the decades and centuries prior to 1800 that the artform of the Mixed Drink was evolving. Instead of recipes for individual drinks, the pattern was to created mixed drink "categories".
March 20, 1798: (as reported by Jared Brown and Anistatia Miller) Apparently the very first mention of the word "cock-tail" as reported in London's "The Morning Post and Gazetteer". There, it recounted how the landlord of the Axe & Gate tavern at the corner of Downing and Whitehall, on winning a share of a lottery, returned to his establishment and erased his regulars’ tabs. The paper provided "a list of the scores that were owing to him by the Nobility and Gentry of the neighborhood". Within the list was an entry for:
- Mr. Pitt, two petit vers of "L'huile de Venus"
ditto, one of "perfeit [sic.] amour"
ditto, "cock-tail" (vulgarly called ginger)
- Mr. Pitt, two petit vers of "L'huile de Venus"
Exactly what said "cock-tail" consisted of is unknown, and may, or may not, have been alcoholic.
Dawn of the Cocktail (1800 to 1860)
The cocktail comes onto the scene in the beginning of the 1800's and very gradually begins to get noticed. The concept of "mixed drink categories" was still prevalent, but over time would loose its luster.
- "11. Drank a glass of cocktail — excellent for the head ... Call'd at the Doct's. found Burnham — he looked very wise — drank another glass of cocktail."
May 6, 1806, "The Balance & Columbian Repository" provides one of the first mentions of the "cock-tail".
The BALANCE and COLUMBIAN REPOSITORY
HUDSON, (NEW-YORK) Tuesday, MAY 6, 1806
May 13, 1806: The earliest known "definition" of what a "cock tail" is was published in "The Balance and Columbian Repository". The editor, in responding to a query from a reader, provided the following definition  (emphasis added):
The BALANCE and COLUMBIAN REPOSITORY
HUDSON, (NEW-YORK) Tuesday, MAY 13, 1806
Golden Age (1860 to 1920)
Entering into this era, the cocktail is still just "yet another" mixed drink category, which isn't necessarily seen as being any more important than the others, but that changes quickly. By the end of this time the cocktail is king, to the point of becoming an umbrella category that incorporates many other mixed drink types.
The Criterion Restaurant opens in Piccadilly Circus, London. It includes a bar which is considered to be the first American Bar in London. Its bartender, Leo Engel, swore by the delicious Criterion Milk Punch. 
The earliest (known) reference to "Old Fashioned" being used to refer to a cocktail, comes from the Chicago Tribune, where it was reported that the goal-oriented Democrats downed “Hot-whiskies, … sour mashes and old-fashioned cocktails" in honor of Samuel Tilden's withdrawl from the presidential race. It should be noted that the Pendennis Club in Louisville Kentucky wasn't founded until 1881, so this puts to rest the story that this drink was created there instead.
The Chicago Tribune asked a local bartender what sorts of drinks were currently in vogue, he replied: “The old-fashioned cocktails [are] still in vogue; cocktails made of loaf-sugar and whisky… Rye whiskey [is] called for more than Bourbon.”
Henry Charles ("Carl") Ramos serves the first Ramos Gin Fizz (originally the New Orleans Gin Fizz) at his New Orleans bar, the Imperial Cabinet.
1907: Absinthe is banned in Switzerland.
1909: Absinthe is banned in The Netherlands.
1911: A former bistro in Paris is purchased by a famous American Jockey Tod Sloan. Tod's partner Clancy owned a bar in Manhattan, which was dismantled and shipped to Paris. They named their new bar the "New York Bar", and hired Harry MacElhone, a barman from Dundee, Scotland.
1912: Absinthe is banned in America.
1914: Russian prohibition begins.
1915: Absinthe is banned in France.
December 18, 1917: The 18th Amendment, which would lead to prohibition in the US, was proposed in the US Senate.
Negroni: Sometime during the year 1919, or perhaps early 1920, the "Negroni" cocktail was invented when Cammillo Luigi Manfredo Maria Negroni (reportedly a Count) asked Fosco Scarselli, barman at the Cafe Casoni to "fortify" his regular Americano with some gin. There is a letter from October 13, 1920 written to Count Camillo (at some point he dropped the second "m" in his name) from Frances Harper of Chelsea, London:
January 16, 1919: The 18th Amendment to the US Constitution is certified as ratified, and will go into effect in one year. Many states by this time had already instituted their own version of prohibition locally.
October 28, 1919: The "Volstead Act" is passed by the US Congress, overriding President Woodrow Wilson's veto. It establishes a definition of intoxicating liquor and provides enforcement of Prohibition.
American Prohibition (1920 to 1933)
The "Great Cocktail Lobotomy" descends upon the US. During this decade the art and craft of the cocktail is all but forgotten, in the US anyway. Many American bartenders go to Europe where they can continue serving cocktails.
Need to insert here a list of cocktails which were believed to have been "invented" during American Prohibition, perhaps separate "American" creations from non-American?
January 17, 1920: The 18th Amendment of the United States Constitution goes into effect.
1923: Harry MacElhone buys the "New York Bar" in Paris and renamed it "Harry's New York Bar".
1930: Publication of "The Savoy Cocktail Book" by Harry Craddock, head bartender at the famed Savoy in London. This book is a collection of 750 cocktails, first published in 1930 and is still in print today.
December 5, 1933: Prohibition in the United States was repealed.
Years of Indulgence (1934 to 1968)
With Prohibition over, the general public attempts to reestablish their pursuits of the well turned drink, but too much had been forgotten, and too many bad habits had been formed. The birth of Tiki almost reminds us of the craft of the cocktail, but it eventually becomes a façade of itself. Renewed interest in the Martini tries to remind us of what we had forgotten, but the Vodka Martini turns it into little more than an alcohol delivery vehicle.
Don Beach (born Ernest Raymond Beaumont Gantt) opens a bar called "Don's Beachcomber" in Hollywood California on McCadden Place.
Victor Bergeron opens up "Hinky Dinks" in Oakland California.
The December issue of Esquire Magazine lists the 10 most popular cocktails as:
- Dry Martini
- Ward Eight
- Vodka Cocktail [3 parts vodka, 1/2 part each of Italian and French vermouths]
- Vermouth Cassis
- Champagne Cocktail
- Planter's Punch
- Old-Fashioned Dutch [with gin, but not genever]
- Harvest Moon [applejack sour w/orgeat]
Victor Bergeron's "Hinky Dinks" becomes "Trader Vic's", and Victor takes on the nickname "The Trader".
Popular drinks during this time as listed in "Burke's Complete Cocktail and Tastybite Recipes" by Harman Burney Burke:
- Martini Cocktail (dry or sweet)
- Manhattan Cocktail (dry or sweet)
- Bronx Cocktail (dry or sweet)
- Old Fashioned Whiskey Cocktail (sweet)
- Sidecar Cocktail (sweet)
- Clover Club Cocktail (dry)
- Gin Rickey (dry)
- Gin Fizz (sweet or dry)
- Alexander Cocktai No. 1 (sweet)
- Rock and Rye (sweet)
- Whiskey Cocktail (dry)
- Sherry Cocktail (sweet or dry)
- Dubonnet Cocktail (sweet)
- Champagne Cocktail
Don Beach opens up his first "Don the Beachcomber" restaurant, across the street from his bar "Don's Beachcomber".
Victor Bergeron creates the "Mai Tai". The original recipe was: 2 ounces 17-year-old J. Wray Nephew Jamaican rum, 1/2 ounce French Garnier Orgeat, 1/2 ounce Holland DeKuyper Orange Curacao, 1/4 ounce Rock Candy Syrup, juice from one fresh lime. Hand shake and garnish with half of the lime shell inside the drink and float a sprig of fresh mint at the edge of the glass.
A "Don the Beachcomber" opens up in Waikiki, bringing the "Polynesian" motif, back to... well... Polynesia. Before this time, all traces of the polynesian decor had been effectively exercised from the environment in the name of Progress and Christianity.
Popular drinks during this time:
- Manhattan (favored by both men and women)
- Martini (favored by men)
- Daiquiri (favored by women)
- Whiskey Sour
- Tom Collins
- Cuba Libre
- Rob Roy
- Gin Rickey
- Creme de Menthe Frappe
- Gin Fizz
(the above is a partial list from "The Bartenders Book" by Jack Townsend, published in 1951. This list was arrived at by sending a detailed survey to bartenders across the US and Canada)
The Dark Ages (1969-1989)
The cocktail turns comical. Many eschew cocktails since they see them as "what their parents used to drink", and those who eventually do partake, favor the syrupy sweet beverages which remind them of their childhood.
1969: Joe Gilmore, head barman at Savoy Hotel's American Bar in London, created the "Moonwalk" cocktail in honor of the Apollo 11 moon landing.
- 1 oz. fresh grapefruit juice
- 1 oz. orange liqueur (Grand Marnier)
- 3 drops rose water
- Topped with Champagne
Combine grapefruit juice, orange liqueur, and rose water in an ice-filled shaker. Shake vigorously and strain into a champagne flute; top with champagne.
Age of Rediscovery (1990-2000)
The decade leading up to 2000 saw a slowly growing interest in rediscovering the cocktail. There was a small, but dedicated group of individuals who began to dig into the long forgotten cocktailian craft as it existed prior to Prohibition and would set the stage for giving the cocktail a greater exposure.
Cocktail Revival (2000 to Present)
January 1, 2000: Milk & Honey opens in New York. The bar was created by Sasha Petraske and despite its hidden location, and its "reservations only" requirement, it gained popularity amongst cocktail enthusiasts and soon-to-be craft bartenders.
November 2, 2002: The Zig Zag Café in Seattle reopens, this time with Ben Dougherty and Kacy Fitch as owners. The Zig Zag was the first truly "Craft" cocktail bar in Seattle, and set the standard for many others.
March 3, 2003: "A Tribute to Professor Jerry Thomas" at the Plaza Hotel in New York. Featuring Jerry Thomas cocktails served by Dale DeGroff, Ted Haigh, Robert Hess, George Papadakis, Sasha Petraske, Gary Regan, Audrey Saunders, and David Wondrich. Presented in cooperation with Slow Food NYC.
September, 2003: Tales of the Cocktail was founded as an annual event in New Orleans by Ann Tuennerman. The previous year, Ann hosted the "New Orleans Original Cocktail Tour" which provided a tour through historic New Orleans bars.
October, 2004: The Museum of the American Cocktail is founded by Dale DeGroff, Jill DeGroff, Robert Hess, Philip Greene, Ted Haigh, Anistatia Miller, Jared Brown, Chris McMillian, Laura McMillian.
2005: Regans' Orange Bitters #6 comes to market. This represents one of the first new bitters to be released in modern times, and opened the floodgates for others to follow suit.
The "Estately Blog" apparently used Google Analytics to identify "What’s The Most Popular Cocktail In Each State?" Here is the ranked list of states based on "Cocktail Enthusiasm" along with what their apparently favorite cocktail is:
- Massachusetts: Martini
- New York: Manhattan
- Washington: Old Fashioned
- California: Sidecar
- Illinois: Martini
- Colorado: Pisco Sour
- District of Columbia: Sidecar, Gimlet, Martini
- Louisiana: Sazerac
- New Hampshire: Cosmopolitan
- Wisconsin: Bloody Mary
- Rhode Island: Martini
- Nevada: Tom Collins
- Connecticut: Cosmopolitans
- Pennsylvania: Martini
- Minnesota: Tom Collins
- Maine: Cosmopolitan
- Maryland: Martini
- New Jersey: Martini
- Oregon: Sidear
- Texas: Margarita
- North Carolina: White Russian
- Georgia: Tom Collins
- Vermont: Cosmopolitan
- Florida: Mojito
- South Carolina: Mint Julep
- Arizona: Tequila Sunrise
- Hawaii: Mai Tai
- Montana: White Russian
- Ohio: Long Island Ice Tea
- Tennessee: White Russian
- Kentucky: Mint Julep
- Virginia: Pisco Sour
- Mississippi: Sex on the Beach
- Missouri: Long Island Ice Tea
- Michigan: Sex on the Beach
- Delaware: Cosmopolitans
- Kansas: White Russian
- Oklahoma: Tom Collins
- Alabama: Mint Julip
- Alaska: White Russian
- Indiana: White Russian
- Nebraska: Tom Collins
- Iowa: Sex on the Beach
- New Mexico: White Russian
- Arkansas: Tom Collins
- Idaho: White Russian
- Utah: White Russian
- Wyoming: Bloody Mary
- West Virginia: White Russian
- North Dakota: Long Island Ice Tea
- South Dakota: Sex on the Beach
- The Morning Post and Gazetteer March 20, 1798
- "The Farmer's Cabinet", April 28, 1803
- New Hampshire and the Birth of the Cocktail (Cow Hampshire Blog, March 10, 2011)
- The Origin of the Cocktail, Ted Haigh (Imbibe)
- The Bar-Tenders Guide (EUVS Library)
- Cooler shakers: The return of the cocktail (Independent)
- "Imbibe!", David Wondrich, Perigee Trade (November 6, 2007)
- The Most Influential Cocktail Book To Date, Jason Wilson (The Washington Post)
- Recipes for Mixed Drinks (EUVS Library)
- Luca Picchi, "Sulle tracce del conte. La vera storia del cocktail Negroni", 2006
- Luca Picchi, "Negroni Cocktail, An Italian Legend", Giunti (September 23, 2015)
- 18th Amendment to the US Constitution (Wikipedia)
- The Volstead Act (National Archives)
- The Savoy Cocktail Book, Harry Craddock (Dover, 2018)
- Moonwalk Cocktail (Saveur)
- The Journey Begins, Robert Hess (DrinkBoy.com)
- MSN Groups DrinkBoy Community (Archived December 14, 2001
- Milk & Honey New York website
- A Tribute To Jerry Thomas, Robert Hess (DrinkBoy.com)
- Shaken, Stirred or Mixed, The Gilded Age Lives Again, William Grimes (New York Times)
- Tales of the Cocktail (Wikipedia)
- The Museum of the American Cocktail (Wikipedia)
- The Pegu Club, Frank Bruni (New York Times)
- What’s The Most Popular Cocktail In Each State? (Estately Blog - archived)