The Winnebago River, a tributary of the Shell Rock River, a part of the Cedar River watershed that flows via the Iowa River to the Mississippi River. It flows southeast through Mason City on its way to the Shell Rock River at Rockford.

The Winnebago River was originally known as Lime Creek. With the growing fame of Meredith Willson's Music Man and its mythical River City, locals wanted to promote the creek to a status of a river. In 1961, the U.S. Board on Geographical Names officially changed the name to Winnebago River.

The Winnebago River bridge spans the Winnebago River at U.S. Highway 65. Built in 1926, it is the longest monolithic concrete girdier in Iowa.

The Winnebago River Bridge was placed on the National Register of Historic Places June 25, 1998.