To a certain extent it will always come down to standing on a site, looking it over and saying "Yep, that's where it has to be". But what if there is absolutely nothing to be seen? Well, that is where Sanborn maps can help out. Sometimes.
Sanborn maps are a great source for historical researchers. They were compiled in exquisite, artistic detail by the fire insurance firm of the same name. Their main interest of course is locating flammable things. And in this respect they are a mixed blessing. Breweries were very, very flammable things, so they often got their own detailed map. Caves are just about the definition of non flammable so they were often left off.
Today lets have a look at some maps. What they can show you. What they can't. Or don't.
From Dubuque Iowa is a view of the Glab Brewery.
This is the place where the trusty guard dog "Punch" was buried next to the cave. The notation says No Watchman. Well, with Punch's spirit guarding things one would hardly be needed. Note that the Beer Cellar has a board roof, something I have never seen, and given the rock structure of the area, something that would hardly be expected.
Now here is an example of what is not shown. This is the Argall Brewery in Mineral Point, a continuation of the first brewery in Wisconsin. There is a cave there. I've seen it! But, and this is quite common, it is not shown. But a helpful clue, often the ice house is either above or adjacent to the cave site.
Whether or not brewery caves are shown appears to be very hit and miss, perhaps depending on the inclination of the surveyor. Here are two images from Hudson Wisconsin from the 1884 map.
This one shows the "Casanova" caves in fabulous detail.
And this one is from the other brewery in town, on a site I have looked over twice and with considerable effort. Although it clearly shows "BEER CAVE" I can at this late date see no sign of it. Occasionally destruction efforts were comprehensive even in caves like this which were chiseled into solid rock.
If you want to do you own research on brewery caves, or anything else, your tax dollars have in this instance been put to excellent use. HERE is a link to the appropriate section of the National Archives. Happy hunting, free of cockleburrs and mud!