Wisconsin Historical Society

The Wisconsin Historical Society (still officially the State Historical Society of Wisconsin) is simultaneously a private membership and a state-funded organization whose purpose is to maintain, promote and spread knowledge relating to the history of North America, with an emphasis on the state of Wisconsin and the trans-Allegheny West. Founded in 1846 and chartered in 1853, it is the oldest historical society in the United States to receive continuous public funding. The society's headquarters are located in Madison, Wisconsin, on the campus of the University of Wisconsin–Madison.

More information on the Wikipedia page.

The website is.