The founders of Adams County were from upstate New York. These people were descended from the English Puritans who settled New England in the 1600s. They were part of a wave of New England farmers who headed west into what was then the wilds of the Northwest Territory during the early 1800s.

The area covered by present-day Adams County was historically part of several other counties. In 1840, when Wisconsin was still a territory, Adams County was the southwestern section of Brown County. In 1836, Portage County was created and included most of present-day Columbia County, including the city of Portage, Wisconsin. In 1846, Portage County was renamed Columbia County. The area from the northern boundary of Columbia County to Lake Superior was removed from Brown County and was then called Portage County. In 1848, the southern part of Portage County was renamed Adams County and included all of current-day Adams County and the northern section of Juneau County. Adams County was organized in April 1853. In 1858, The northwestern part of Adams County was joined with the northern part of Sauk County to form present-day Juneau County. At this time, Adams County took its current shape.