<P> The river begins with three separate branches which flow into the Horicon Marsh . The northermost branch , the West Branch , begins just to the west of the village of Brandon in Fond du Lac County , Wisconsin and flows east and then south to Horicon Marsh . The South Branch rises north of Fox Lake in Dodge County and flows east through Waupun to the marsh . The East Branch rises southeast of Allenton in Washington County just west of the Niagara Escarpment , and flows north and west through Theresa to the marsh . Leaving the marsh , it meanders southward to the Illinois border ending about 300 miles later at the Mississippi River at the Quad Cities in Illinois and Iowa . During its course it passes through Watertown , collects the Crawfish River in Jefferson , and receives the Bark River at Fort Atkinson . In northern Rock County it receives the Yahara River , and flows southward through Janesville and Beloit into northern Illinois , where it receives the Pecatonica River 5 miles ( 8 km ) south of the state line . </P>
<P> The river begins with three separate branches which flow into the Horicon Marsh . The northermost branch , the West Branch , begins just to the west of the village of Brandon in Fond du Lac County , Wisconsin and flows east and then south to Horicon Marsh . The South Branch rises north of Fox Lake in Dodge County and flows east through Waupun to the marsh . The East Branch rises southeast of Allenton in Washington County just west of the Niagara Escarpment , and flows north and west through Theresa to the marsh . Leaving the marsh , it meanders southward to the Illinois border ending about 300 miles later at the Mississippi River at the Quad Cities in Illinois and Iowa . During its course it passes through Watertown , collects the Crawfish River in Jefferson , and receives the Bark River at Fort Atkinson . In northern Rock County it receives the Yahara River , and flows southward through Janesville and Beloit into northern Illinois , where it receives the Pecatonica River 5 miles ( 8 km ) south of the state line . </P>
where is the origin of the rock river
where is the origin of the rock river
Horicon Marsh
Horicon Marsh