The Coow Woow is purported to be the oldest cocktail in America. I found it at the Wayside Inn in Sudbury, where it shares a tent-card in the tavern with the Stonewall, under the breathless claim 'The oldest cocktails in America","found on a document from 1664" and lots of marketing-style hyperbole.
Diligent research has been largely fruitless. The historian from Plimoth Plantation had no knowledge of the drink or of any 1664 document that could be expected to contain the formula for this potion. The bartenders at the well-qualified No. 9 Park and Locke-Ober have no knowledge of it. Somewhere on the internet I saw the claim that "Coow woow" was an Indian term for rum, but I found nothing else to substantiate it.
By far the most information on the internet relating to Coow Woow come from newspaper reviews of the restuarant and derivatives of such reviews, all quoting verbatim or near-verbatim from that tent-card at the Wayside Inn. The Coow Woow may be nothing more than the fevered imaginings of a bored barkeep and his girlfriend from Marketing!
Anyway, the Coow Woow is not great, but it is pretty good once you know what you are getting into. The one I tried at the Wayside Inn was made with white rum, but I tried it later at the Old Colony Club with dark rum and found it superior. The members who partook in my alchemical pursuits were pretty well unanimous that it is very tasty, but mighty strong.
Note that it is all liquor - no mixers, no ice, no mercy. In my opinion, one of its best uses would be as an additive to a non-alcoholic ginger-ale based punch, maybe especially a ginger-cranberry punch.
My researches have been diligent and thorough. They finally led to master mixer and cocktail historian John Gertsen at Drink, a bar in Fort Point, Boston, just a few blocks from South Station. It seems the Coow Woow has no provenance outside the Wayside Inn in Sudbury, where it is a celebrated part of the menu.
Gertsen agreed with my suspicion that it may well be an invention of the Wayside Inn marketing department. He offered that it may well be based on local lore, that the mixture of rum and ginger brandy was certainly possible in the colonial environment and the 2:1 mixture may have been a common way to drink it even with no "official name" in the days before mass marketing required everything to be a "product" with a name.
So there you have it. If you learn any more on this subject, do please post it here!