The Idaho Transportation Department (ITD) is responsible for the establishment and classification of a state highway network, including 5,000 miles (8,000 km) of roads that are classified as Interstate Highways, U.S. Highways, and state highways within the state of Idaho in the United States.[1] The current state highway marker consists of a white background, black numbering, and a solid black geographic outline of the state of Idaho.
During the 1920s, in lieu of numbering its highways, Idaho had a system of lettered Sampson Trails.[2] They were marked by businessman Charles B. Sampson of Boise at no expense to the state, using orange-colored shields.[3] By 1929, the trails system had included 6,500 miles (10,500 km) of marked highways that covered most of the state.[4] By the mid-1930s, the state had adopted a more standard system of numbered state highways.[5][6]
In 1978, the ITD began using brown state highway markers to denote scenic Idaho highways,[7] in addition to the main highway markers that featured a black background and white lettering and the name "IDAHO" in black lettering inside a white geographic outline of the state. The brown markers were discontinued around 2012, and in April 2020, ITD changed the coloring of the main state highway marker to its current color scheme, also adding a wide version of the marker for three-digit highways and removing the word "IDAHO" from all markers in the process.[8]
^ abRand McNally Auto Road Atlas, 1926, accessed via the Broer Map Library
^Senate Concurrent Resolution No. 8, "a concurrent resolution...to permit Charles B. Sampson to extend the marking system of the Sampson Trail..." passed February 16, 1933
^Lawson, H. A. (March 25, 1929). "Blazing Western Trails is Unique Hobby of Idahoan". Daily Herald. p. 3. Retrieved April 21, 2019 – via Newspapers.com.
^"Colored US highway shields". US ends .com. April 5, 2020. Retrieved April 26, 2020.
^"Traffic Manual: Idaho Supplementary Guidance to the MUTCD" (PDF). Idaho Transportation Department. April 2020. pp. 37–38, 60. Retrieved April 26, 2020.
^"Milepoint Logs". Idaho Transportation Department. Archived from the original on February 16, 2017. Retrieved February 15, 2017.
^Downing, T.A. (April 15, 1937). "Designated Federal and State Highways Minute Book 09". Idaho Bureau of Highways. Retrieved October 3, 2018 – via Idaho State Archives.
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