About the Wisconsin Trunk Highway System
Wisconsin was the first place in the world to number its highways. The numbered system was enacted in 1917 to replace the unofficial auto trails that were cluttered and confusing for motorists. The numbered system made it easier for motorists to travel, and was soon adopted by the rest of the nation and the world.
Wisconsin also has a unique lettered county road system. Started in the 1920s, counties laid out a lettering system for their maintained roads. Eventually adopted by the state, the letter designations can be 1,2, or 3 characters long. Lettered routes can be used multiple times throughout the state.
County trunk highways can be lettered just to give a road a designation, or they can can have meaning. For example, County HS in Brown County was named because it passes through Howard and Suamico.