The Saint Croix was one of the original eight rivers protected when the Wild and Scenic Rivers Act became law in October 1968, and it remains the largest wild and scenic river system east of the Mississippi. The unit preserves approximately 200 miles: the upper St. Croix River along the Minnesota-Wisconsin border down to Taylors Falls, together with its major tributary the Namekagon River, which flows 98 miles entirely within northwestern Wisconsin. The designation came out of legislative work by Senators Walter Mondale of Minnesota and Gaylord Nelson of Wisconsin (the founder of Earth Day); their home states' cooperation shaped what a wild and scenic river could mean in practice. The corridor is notable for remaining connected to its floodplain - a rarity for a river of this size in the industrial Midwest - and for how fully undeveloped it feels despite its proximity to the Minneapolis-Saint Paul metro. The St. Croix and Namekagon pass through a north-woods mosaic of white pine, cedar, hardwoods, and wetlands across eight Wisconsin counties and three Minnesota counties, with adjoining state parks and state forests (Governor Knowles State Forest, St. Croix State Forest, Wild River State Park, among others) adding further protected acres. Deer, beaver, otter, eagle, osprey, and timber wolf all live in the corridor, and tens of thousands of mounds built by Woodland-period tribes sit on the bluffs above the river. Dakota and Ojibwe presence here is deep and continuous. The deeper geological story is unusual. About one billion years ago the North American continent began to split apart along the Midcontinent Rift. The rift failed before splitting the continent, but not before vast basalt flows cooled into the hard black rock now exposed in the Dalles of the St. Croix - the sheer basalt cliffs and glacially carved potholes at Interstate State Park near Taylors Falls. Cambrian sandstones and Ordovician carbonates overlie the basalt in many places, laid down 500 million years ago when a vast inland sea covered the region. Paddling is the central use. The upper St. Croix and the Namekagon offer Class I-II canoe and kayak water through forested corridors, with more than 70 NPS-designated primitive campsites reachable only by water. The upper St. Croix is a nationally recognized smallmouth bass fishery; the upper Namekagon above Hayward is known for brown and brook trout. Tubing, motorized boating (on downstream sections), hunting on state lands, and winter cross-country skiing round out the uses. Headquarters and main visitor center are in St. Croix Falls, WI, with a seasonal Namekagon River Visitor Center in Trego, WI.