[4] WisDOT also develops and maintains some minor routes, under the designations of Scenic Byways and Rustic Roads.

The various cities, towns, and villages of the state each maintain their own roads beyond this, servicing individual homes and businesses and connecting them to the other systems, although these are not typically referred to as highways.

In the early 19th century, wagon roads were created so that people and supplies could be transported from one settlement to another in days rather than weeks.

[10] However, by the end of the 19th century, particularly before the popularization of the automobile, railroads became dominant and largely supplanted the state's roadways as means of long-distance transportation.

After approval by the state legislators, an amendment was passed allowing Wisconsin to use funds for highway construction, in 1908.

[11] In 1911, the Wisconsin Highway Commission was established as a central planning organization for the state's first motorized roadways.

The state legislature made this practice illegal in 1917, in a law that also provided for the creation and marking of a state trunk highway system, that would be required to provide access to every county seat and all towns with a population over 5,000 and was limited to a total length of 5,000 miles (8,047 km).

[15] The distinctive route marker was eventually redesigned and codified to be the union of an inverted triangle and a rounded rectangle in 1933; this shape remains in use today.

As a result, the goals of the state highway system were expanded, aiming to reach every town with a population over 2,500 and relaxing its previous upper bound on network length.

The commission proposed various projects, including one from the Illinois border, extending through Madison, and terminating in La Crosse.

The plan classifies the state's highways into five categories based on their importance to the successful functioning of the network as a whole:[20]