The first place we visited upon arrival in the Milwaukee area for the weekend was the Miller Valley. We took the Miller Brewing plant tour. It was about an hour long and was free.
The tour starts in the visitor center with a short video followed by a walking tour outside, then in and out of several buildings (canning, shipping, brewing).
The tour ends in the old storage caves, then into a lodge-like bar for a beer sample, then across the street for a few more samples.
They produce 500,000 cases of beer each day. They also contract brew for other non-miller brands (Pabst, Schlitz, Schmidt and many others).