Wisconsin pioneered the concept of numbered highways. A 1917 state law creating a State Trunk Highway System included a provision requiring uniform guide and warning signs.

Early Wisconsin highway markers could be found on telephone poles, other roadside posts and culverts.

Cutting grass along a Trempealeau County roadway, 1925.

Mowing along a Dane County road, 1940s.

I-94 under construction between Hudson and Menomonie in western Wisconsin in October, 1958. A year later (October 29, 1959), a ceremony was held dedicating the 59-mile segment of I-94 between Hudson and Eau Claire. It represented, at that time, the nation's longest single section of Interstate highway to be officially dedicated.

Climbing lane along "Coon Valley Hill" on US 14 in Vernon County, 1959.

I-94 under construction west of Oconomowoc in Waukesha County in November 1963. The first section of Interstate highway to be completed in Wisconsin was a one-mile segment of I-94 near Johnson Creek in Jefferson County in 1958.

Looking eastward at the Stadium Interchange in Milwaukee, February 1964.

Hill Farms State Transportation Building, Madison - completed July 1964.

Wisconsin Governor Warren Knowles cuts the ribbon on the final section of I-94 in Jefferson County on October 27, 1965, creating a continuous 78-mile Interstate route between Madison and Milwaukee.

Wisconsin Governor Warren Knowles speaks during the ribbon-cutting ceremony for the final section of I-94 in Jefferson County on October 27, 1965.

Rest area south of Portage along I-90/94 in June of 1967. Wisconsin was one of the first states to provide Interstate rest areas. Currently, Wisconsin is home to 30 rest areas that are widely acclaimed for their amenities and cleanliness.

Merrimac Ferry, Colsac II, August 1967.

On June 13, 2011, to commemorate the 100-year anniversary of a Wisconsin transportation agency, several Wisconsin Department of Transportation secretaries gathered at the Hill Farms State Transportation building in Madison. Sitting left to right: Chuck Thompson, Ron Fiedler, Owen Ayres and Dale Cattanach. Standing left to right: Mark Gottlieb, Tom Carlsen, Gene Kussart and Terry Mulcahy.