WIS 138 starts in Cooksville, an unincorporated community with an Evansville address. It runs north into Dane County towards Stoughton, although it makes one S-bend on the way. In Stoughton, it turns west with US 51. It runs concurrently with US 51 to the west side of the city, then continues west in a straight line towards Oregon. It becomes Janesville Street once it crosses US 14.[2]
History
Starting in 1923, WIS 138 was formed to travel roughly along its present-day route from WIS 10/WIS 106 (now US 51/WIS 138) in Stoughton to WIS 59 in Cooksville.[3][4] Up until 1962, no major change to the routing had happened. Then, WIS 138 superseded part of WIS 106 from Stoughton to US 14 near Oregon.[5][6] In late-1978, US 14 was moved onto a newly built expressway around Oregon. As a result, WIS 138 no longer needed to travel southwestward to get to US 14. Instead, it then continuously traveled westward to get to US 14.[7][8]
Major intersections
This section is missing mileposts for junctions. Please help by adding them.
^State Highway Commission of Wisconsin (1962). Wisconsin Highway Map(PDF) (Map). c. 1:538,560. Madison: State Highway Commission of Wisconsin. OCLC12359573. Retrieved March 21, 2021 – via Wikimedia Commons.
^State Highway Commission of Wisconsin (1963). Wisconsin Highway Map(PDF) (Map). 1:823,680. Madison: State Highway Commission of Wisconsin. Retrieved March 21, 2021 – via Wikimedia Commons.
^Wisconsin Department of Transportation Division of Highways (1978). Wisconsin Highway Map(PDF) (Map) (1978–1979 ed.). 1:823,680. Madison: Wisconsin Department of Transportation. OCLC174123957. Retrieved March 21, 2021.
^Wisconsin Department of Transportation Division of Highways (1980). Wisconsin Highway Map(PDF) (Map) (1980–1981 ed.). 1:823,680. Madison: Wisconsin Department of Transportation. OCLC613423704, 77526920. Retrieved March 21, 2021.