The roadway has been a part of the state's primary highway system since its inception in 1920; however, it has only been known as Iowa 139 since 1930.

The highway curves to the east, fully entering Winneshiek County, and then back to the north.

Rising out of the valley, the road curves to the north and remains in its heading until just before the Minnesota state line.

20), which was a north–south route that passed through Decorah, Dubuque, Davenport, Fort Madison, and Keokuk.

[10][11] In 1980, the Protivin spur was turned over to Howard County, where today it is CR V58.