At one time or another we have all questioned what county a particular town was in historically. That is important, of course, because the county of residence will dictate what courthouse vital records will be found in. If a city changes affiliation from county A to county B in 1855, then vital records and legal documents will be filed in the new courthouse from that date forward, while documents before that date will continue to reside in the county A's courthouse.
There is some software that can help us trace the changes of county lines over time. One of those programs is Animap <http://www.goldbug.com/AniMap.html> at a price of about $85.
But there is a website that can be of help also. It is <http://jrshelby.com/hcl/>. This site refers you to related sites depending on the county in question. Some of the sites are free and some may be fee-based.
Nosing around a bit I found a Wisconsin map dated 1857 from a collection kept at the University of Alabama. It was easy to find and it was free.