Wisconsin’s Department of Transportation has released scans of every edition of its official state highway map back to 1918.1 Available for download at that link. Also available for download: this 12-page guide discussing the evolution of the state’s highway map (PDF). It covers all sorts of paratextual things such as safety messaging, the governor’s welcome message, tourism and slogans in addition to the development of the map itself. Well worth a read.
The most recent map available at the moment is the 2019-2020 edition; a 2023 edition of the map is at the printer’s and will be released this summer.
Previously: Historical Highway Maps of Manitoba.