The Northern Hospital for the Insane, founded in 1873 and operated by the state of Wisconsin, is now called the Winnebago Mental Health Institute. Don't be scared off by the name, they sent folks to "the Northern" for everything from postpartum depression to Alzheimer's, etc. They DO have records all the way back, but you have to write and explain how you are related etc. Even long deceased patients have a right to privacy.
Across the road to the west are the Winnebago County poor farm, hospital, asylum, Sunnyview TB sanatarium, varying names for varying configurations at varying dates from the early 1870s on. This is the cemetery whch is being researched at present. Although this was run by the county, at some times they took patients from other counties nearby on a contract basis.
So how do you know they were there, and when was it?