|• location||Lac Vieux Desert|
|• elevation||1,683 ft (513 m)|
|Mississippi River near Prairie du Chien, Wisconsin|
|Length||420 mi (680 km)|
|Basin size||12,280 sq mi (31,800 km2)|
|• average||12,000 cu ft/s (340 m3/s) at mouth|
|Official name||Lower Wisconsin Riverway|
|Designated||14 February 2020|
The Wisconsin River is a tributary of the Mississippi River in the U.S. state of Wisconsin. At approximately 430 miles (692 km) long, it is the state's longest river. The river's name, first recorded in 1673 by Jacques Marquette as "Meskousing", is rooted in the Algonquian languages used by the area's American Indian tribes, but its original meaning is obscure. French explorers who followed in the wake of Marquette later modified the name to "Ouisconsin", and so it appears on Guillaume de L'Isle's map (Paris, 1718). This was simplified to "Wisconsin" in the early 19th century before being applied to Wisconsin Territory and finally the state of Wisconsin.
The Wisconsin River originates in the forests of the North Woods Lake District of northern Wisconsin, in Lac Vieux Desert near the border of the Upper Peninsula of Michigan. It flows south across the glacial plain of central Wisconsin, passing through Wausau, Stevens Point, and Wisconsin Rapids. In southern Wisconsin it encounters the terminal moraine formed during the last ice age, where it forms the Dells of the Wisconsin River. North of Madison at Portage, the river turns to the west, flowing through Wisconsin's hilly Western Upland and joining the Mississippi approximately 3 miles (4.8 km) south of Prairie du Chien.
The highest waterfall on the river is Grandfather Falls in Lincoln County. It creates the borders between Adams, Juneau, Columbia, Sauk, Dane, Iowa, Richland, Grant, and Crawford Counties, creating the only natural county borders within the state (excluding the Mississippi River and the Great Lakes).
The modern Wisconsin River was formed in several stages. The lower, westward-flowing portion of the river is located in the unglaciated Driftless Area, and this section of the river's course likely predates the rest by several million years. The lower reach of the river is narrower than its upstream valley, leading to the suggestion that the upper portions of the ancestor of the river flowed east before the Pleistocene. The remaining length of the river was formed gradually as glaciers advanced and retreated over Wisconsin. The stretch of river from Stevens Point north to Merrill was a drainage route for meltwater flowing away from the glaciers which covered northern Wisconsin during the Wisconsin Glaciation. As the glaciers retreated further northward, the river also grew in that direction. South from Stevens Point, the meltwater would have flowed into Glacial Lake Wisconsin, a prehistoric proglacial lake that existed in the central part of the state. As temperatures warmed around 15,000 years ago, the ice dam holding the lake in place burst, unleashing a catastrophic flood that carved the Dells of the Wisconsin River and joined the upper stretches of the river with the pre-existing lower river valley that today flows from Portage to Prairie du Chien.
In the summer of 1673, French missionary Jacques Marquette, French-Canadian explorer Louis Joliet, and their crew of five Metis arrived near the headwaters of the Fox River. From there, they were told to portage their two canoes a distance of slightly less than two miles through marsh and oak plains to the Wisconsin River.
The first documented exploration of the Wisconsin River by Europeans took place in 1673, when Jacques Marquette and Louis Jolliet of France canoed from Lake Michigan up the Fox River until they reached the present-day site of Portage in early June. At this location the Wisconsin and Fox rivers are only 2 miles (3.2 km) apart, so the explorers could portage from the Fox to the Wisconsin River. They then continued downstream 200 miles (320 km) to the Wisconsin's mouth, entering the Mississippi on June 17. Other explorers and traders would follow the same route, and for the next 150 years the Wisconsin and Fox rivers, collectively known as the Fox-Wisconsin Waterway, formed a major transportation route between the Great Lakes and the Mississippi River.
Industry began to form on the Wisconsin in the early 19th century, as loggers started using the river to raft logs downstream from northern forests to sawmills in new cities like Wausau. By the 1880s, logging companies were damming the river to ensure the river had enough capacity for the logs being floated downstream. Later, at the start of the 20th century, more dams were constructed to provide for flood control and hydroelectricity. The dams also spurred tourism, creating reservoirs such as Lake Wisconsin that are popular areas for recreational boating and fishing. Today the Wisconsin River is the hardest working river in the nation. There are 25 operating Hydroelectric Power Plants on the Wisconsin River. The "hydros" harness 645 feet of the rivers fall to generate nearly one billion kilowatt hours of renewable electricity a year — enough energy to supply the residential needs of over 300,000 people without creating any pollution.
Despite this, a 93-mile (150 km) stretch of the Wisconsin between its mouth and the Prairie du Sac Dam is free of any dams or barriers and is relatively free-flowing. In the late 1980s, this portion of the river was designated as a state riverway, and development alongside the river has been limited to preserve its scenic integrity.
The Lower Wisconsin River State Riverway is a state-funded project designed to protect the southern portion of the Wisconsin River. It extends 93 miles (150 km) from Sauk City to the point where the Wisconsin River empties into the Mississippi, about 3 miles (4.8 km) south of the city of Prairie du Chien. The Wisconsin Department of Natural Resources manages protected lands of over 75,000 acres (300 km2), including the river itself, islands, and some lands adjacent to the river. In 2020 the riverway was designated as a protected Ramsar site.
There are no dams or man-made obstructions to the natural flow of water between the hydroelectric dam just north of Sauk City and the confluence of the Wisconsin and the Mississippi. This long stretch of free-flowing river provides important natural habitats for a variety of wildlife, including white-tail deer, common otters, beavers, turtles, sandhill cranes, eagles, hawks, and a variety of fish species.
Recreational opportunities on the lower Wisconsin River range from fishing and canoeing to tubing and camping. Canoe camping is particularly popular because of the abundance of suitable sandbars along the riverway and because no permits are required. On summer weekends, naturists can be found on Mazo Beach which is north of the village of Mazomanie. According to the Wisconsin Department of Natural Resources, two thirds of river users can be found on the stretch between Prairie du Sac and Spring Green.