| State: | WI |
| Type: | WI |
| Route: | 138 |
| Map Custom: | yes |
| Map Notes: | WIS 138 highlighted in red |
| Length Mi: | 13.23 |
| Length Ref: | [1] |
| Length Round: | 2 |
| Direction A: | South |
| Direction B: | North |
| Terminus A: | in Cooksville |
| Junction: | in Stoughton |
| Terminus B: | in Oregon |
| Counties: | Rock, Dane |
| Previous Type: | WI |
| Previous Route: | 137 |
| Next Type: | WI |
| Next Route: | 139 |
State Trunk Highway 138 (often called Highway 138, STH-138 or WIS 138) is a state highway in the U.S. state of Wisconsin. It runs west - east between Oregon and Stoughton and north - south between Stoughton and Cooksville.
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.
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.[2] [3] 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 Then, WIS 138 superseded part of WIS 106 from Stoughton to US 14 near Oregon.[4] [5] In late-1978, US 14 was moved onto a newly built expressway around Oregon.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.[6] [7]