Jeff Renner kindly drew my attention to an online version of what brewing historians call the "Handy-book", a circa 1909 book by Wahl & Henius, two American brewing experts. The full title of the book is quite long but for short we can call it a "Handy-book of the Brewing and Malting Trades". It is a fascinating book, one I've known about for years but have never read until I learned it was put online to assist homebrewers and others interested in period recipes and brewing techniques. In perusing this learned text I found on page 818 a description of "Kentucky Common Beer". This was associated in particular with Louisville. The beer was 70% malt and 30% corn (no surprise there) and made with pale malt but had roasted malt added or actual caramel to lend a dark colour. Wahl and Henius state it was consumed by the "laboring classes". The beer was (unlike California Steam beer, also extensively described in the book) top-fermented and wasn't krausened, i.e., it was fermented once and sent out for sale which meant the gravity would be moderate, the carbonation low and the taste full and sweetish. It was probably like a modern English draught mild ale. It may have been (seeing the German origins of many American brewers of the time as the authors' names make clear) a form of kolsch or altbier, German beers that are top-fermented. The beers were racked after a few days in the fermenter and left on troughs for the excess yeast to course out until fermentation stopped (this took two days, the authors say if you want more carbonation in the beer, leave it on the troughs one day!). The trough process sounds a lot like the Burton Unions system of clarifying beers. The authors say the beer still could be turbid if served in "saloons" too soon but left to settle for a few days should be relatively clear. I previously understood California Steam Beer was the only indigenous U.S. beer style, maybe Kentucky Common Beer is not considered such because it was an all-top fermented beer and also, it is (as far as I know) defunct.
The book can be accessed at www.hbd.org/aabg/wahl/. Page 818 is in the section headed "Brewing Operations", look under "Top-fermentation beers in the U.S.".
I thought this would interest Jeff Yeast in particular.