For hardcore coffee-drinkers, a chosen brand is as personal as a favored sports team. Americans drink an average of 25 gallons of coffee a year, but not all java is created equal. Wars have been waged over brews in the past, and while today’s state of affairs is more diplomatic than the Prussian coffee revolt of 1785, skirmishes rage in all 50 states. Thanks to Aggdata‘s store location data, Google Maps, and O’Reilly’s Data Mashups In R, we can map the movements of two fierce warriors – Starbucks and Dunkin Donuts -  and take snapshots of the struggle for caffeine dominance.

Coffee photo by striatic@flickr

The map of the continental United States shows vast expanses of the west dominated by Starbucks, while Dunkin’ Donuts clings to its ancestral home on the east coast. Significant stretches are deprived of both the Pike Place Roast as well as the Coolata.

The large cities of the west coast are dense with green. San Diego, CA is home to the ZIP code with the greatest number of Starbucks (23 of them and not single place to get a Dunkin’ Iced Caramel Latte). Despite the predominant color on the western frontier, Dunkin’s creme-filled crullers and Box O’ Joe manage to hold their own in Vegas and Phoenix.

The Bay Area is an emerald patch, although it should be noted that a significant number of indie coffee shops are left out of this view, not to mention regional favorites such as Peet’s, which has several dozen locations in the area.  The bears in  the wilderness reserves and state parks don’t seem to be drinking any coffee, though.

A 6-hour flight away, the northeast is clearly Dunkin’ land, but a swath of Starbucks presence stretches from Cleveland to the dark, concentrated green of in Washington, D.C, where locals indulge in their Doubleshots.

The heart of New England shines orange, and Massachusetts is home to Brockton, where ZIP 02301 wins the prize for the most Dunkin’ Donuts in the U.S., numbering 16. Brockton has a single Starbucks, and the green dots have consistently crept in greater numbers into Boston itself as well.

In the New York City Area, Manhattan appears as a Starbucks fortress fighting off a Dunkin’ infiltration. At JFK airport, 5 Starbucks stand guard against a Dunkin’ stalking the gates.

Airports facing Starbucks dominance might be a common theme. A ZIP code surrounding Chicago O’Hare, 60666, wins the prize for the biggest Starbucks-to-Dunkin’ ratio of ZIP codes with both stores. A single Dunkin’ Donuts fends off 17 Starbucks. The greater Chicago area is a battleground where southern Wisconsin’s Starbucks presence holds its own against the Dunkin’ hordes that prevail south of Oak Lawn.

The South of the U.S. is a patchwork coffee battleground. In North Carolina and Florida, Dunkin’s munchkins rule, while the Java Chip Frapuccino clusters in the metropolitan cores. Westward, the landscape becomes green, but some holdouts remain. Just outside the New Orleans core, a single Dunkin’ Donuts stands firm, the only one in Louisiana amidst the 64 Starbucks.

The war over your morning brew is just getting started. Dunkin’ Donuts is reportedly considering an IPO worth upwards of $500 million later this year, and others are pursuing the thirsty U.S. market. Tim Hortons, Canada’s “coffee-and-donuts king” is eyeing the U.S. as a prime growth opportunity.

Who do you root for in the coffee wars?