The population of the US was about 63 million in 1890. Since there were 2,011 breweries in 1890, that meant there was 1 brewery for every 31,000 people. With todays population being 312 million, each brewery is supporting about 146,000 people. I suppose most of that is supplied by the big 3 though. We still have room to grow even if we don't party like its 1899.
Thanks for providing some context to these numbers.