I used to work for Winnebago County at the Parks Department. Most of my time was spent at the park or the fairgrounds doing maintenance and ground work. Towards the end of my employment there, due to my position as a seasonal worker, I was told that the grounds were formerly the site of the Winnebago County Poor Farm, Insane Asylum, and the Sunny View Sanatorium. Work got a lot more interesting after that!
Past & Present Aerial View of Grounds

Wisconsin Historic Aerial Image Finder
Map Legend:
1- State Hospital Railroad Depot
2- Winnebago County Insane Asylum
3- Winnebago County Poor Farm
4- Winnebago County Poor House
5- Sunny View Sanatorium
6- Northern State Insane Asylum (Winnebago Mental Health Inst.)
7- Cemetery
Winnebago County established a county program in 1865 to care for the poor and mentally ill. A poor farm, which housed the poor and insane, was built north of town on 125 acres of land in 1871. The facility included barns and other buildings for farm use and a single brick building for the poor to reside. That same year, just east of the poor farm, the State of Wisconsin started construction on the Northern Hospital for the Insane on Lake Winnebago. By 1893 a separate building, the Winnebago County Insane Asylum, was constructed on the county grounds to separate the poor and mentally ill.

Winnebago County Album

On the other side of street, where the Winnebago County Fairgrounds are, was the Sunny View Sanatorium. Sunny View was built to care for those suffering from tuberculosis. Constructing of the hospital began in 1914 and finished sometime in 1915. The hospital closed its doors in September 1971. Some buildings were demolished, and others were used as offices for county departments for a number of years before being demolished.
The original asylum and poor house are long gone; lost to fires and the wrecking ball. Remnants of the farm buildings still stand on Butler Avenue. Over on the fairgrounds side are some buildings of the old Sunny View Sanatorium. Garages once built for staff vehicle are used as maintenance sheds today. The old cemetery is still there, and the dead are marked by numbered, cement markers.
For more in-depth reading about these institutions: