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State and County Trunk Highway System

State Trunk Highways

In 1917 the state legislature directed the State Highway Commission to establish a State Trunk Highway (STH) system that would connect every county seat and city with a population of 5,000 or more and not exceed 5,000 miles.  In order to lay out this new system, a tentative system of desirable routes was mapped, surveyed, and analyzed, and public hearings were held.  Important considerations in determining the final route selection included populations served, the alignment and grades of existing routes, and the supply of local deposits of minerals and aggregates that would be used in construction.  The entire 5,000-mile system was laid out on existing roads with varying surface types, including unimproved sand surface, earthen, gravel, macadam, concrete, brick, and asphalt.

In 1917 Wisconsin became the first state in the country to adopt a uniform road-numbering system.  Rather than the named routes and various unofficial signage, the highways were marked with an inverted triangle with the words "State Trunk Highway" and the route number.  The state also created standard black-and-white signs warning of curves, railroad crossings, and other hazards.  Originally, STH routes were numbered from 10 through 75.  As the system expanded, route numbers through 199 were assigned.  Routes numbered greater than 199 are recent designations that typically run along decommissioned or relocated routes.  In 1925 the American Association of State Highway Officials, following Wisconsin's system, adopted a numbered-highway system for the entire country.


Replacing gravel and pavement
on STH 70, west
of Minocqua, in 1968.
Courtesy of the Wisconsin
Department of Transportation,
Bureau of Environment,
District 7 file.

In 1919 the Wisconsin legislature directed the State Highway Commission to select and add an additional 2,500 miles to the existing 5,000-mile STH system.  In 1923 the legislature authorized additional mileage to the system, not to exceed a total of 10,000 miles.  This provision allowed the system to connect communities of 2,500 or more.  The counties were responsible for the maintenance of highways outside communities and cities were responsible for the maintenance of the connecting streets within cities.

The US Highway (USH) system was implemented in 1926.  The USH system is for marking and numbering purposes only, guaranteeing that a highway will maintain a uniform number as it crosses state lines.  Each state is still responsible for all but a very small portion of the highway maintenance and the USH designation does not provide for additional funding.

Several roads that had been part of the STH system were incorporated into the USH system shortly after its implementation.  Today, Wisconsin is home to 14 USHs (2, 8, 10, 12, 14, 18, 41, 45, 51, 53, 61, 63, 141, and 151).  With the advent of the interstate system, only one USH was decommissioned - USH 16.

County Trunk Highways

The most important early step in the improvement of Wisconsin roads was the county aid highway laws of 1907.  Under these laws any town could make an appropriation for road improvements and receive a monetary match from the county.   The county was required to select the system of highways on which the improvements were to be made and elect a county highway commissioner to carry out the improvements.  Although only about 20 counties initially participated in the program, it created significant improvements over the earlier road conditions.


Continuous paving operation
on USH 14 between
Arena and Plain in
Dane County, 1937.
Courtesy of Wisconsin Historical
Society Archives
(PH Series 2706)

Between 1918 and 1925 county boards continued to add roads to the highway system and many laid out County Trunk Highway (CTH) systems without legislative support.  In 1925 the CTH system was formally established by the legislature as a secondary highway system.  County boards or highway committees were responsible for laying out the system.  Any CTH systems laid out prior to legislative approval were recognized as part of the official system.  Each county board was responsible for conferring with neighboring county boards to ensure that the respective CTHs joined and made continuous lines of travel between the counties.  Uniform signs were used to mark the system across the state and each county board was responsible for marking, signing, and maintaining the roads in their county as well as the bridges on the highways.  CTHs are designated by letters instead of numbers and can be one, two, or three letters in length.

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