They weren't the only brewers around, though. Milwaukee had 23 brewers before it had been a city for 23 years, but only 4 or 5 were ever the Milwaukee Beer Barons. Milwaukee did have the first mass brewery in the US, though, and I think before we were even a state. It shipped along the Great Lakes, especially Chicago.
What's really interesting is prohibition and it's influence on all these old brewers. Wisconsin passed a referendum allowing sale of 'near' beer, something like a 2% by weight cap. Some went to soda and stuff, a really old brewer(1850's) I grew up by sells as much or more soda than they do beer. They make it all in the same little brewery.

If you know Leinenkugel's, I think they survived by bottling and shipping water. I should find the article, but when prohibition was lifted I think the mayor led a city wide party in Milwaukee.
