It ran through 40.1 miles (64.5 km) of Manitowoc, Calumet, and Fond du Lac counties.

[1][2] In 1938, part of the route near Kiel was straightened to follow today's County Trunk Highway XX (CTH-XX).

[3][4] In 1947, WIS 149 was extended westward to US 151/WIS 55 (now just US 151) in Peebles, superseding CTH-U, CTH-I, and a part of CTH-HH.

Also, WIS 149 was extended eastward via Westvie Street and Washington Street to present-day CTH-LS just west of the shore of Lake Michigan.

As a result, CTH-XX extended west to WIS 67 near Kiel.