It originates in southwestern Winneshiek County and flows through southern Allamakee County, receiving tributaries from northern Clayton County, before joining the Mississippi near Marquette and Effigy Mounds National Monument.

The watershed is located in northeastern Iowa's unglaciated Driftless Area.

The catchment measures 154,666 acres (625.91 km2) and is mainly state forest or farmland.

Effigy Mounds National Monument has also grown, either by direct purchase or from gifts.

This article related to a river in Iowa is a stub.