Interstate State Park - Oldest Park
Steep-sided Gorge at the Dalles of the St. Croix River
A steep-sided gorge called the "Dalles of the St. Croix" is the scenic focus of Wisconsin's oldest state park, Interstate State Park. The park's Ice Age Interpretive Center features a 20-minute film, photographs, murals and other information about the great glaciers.
The Park consists of two adjacent state parks on the Minnesota-Wisconsin border, both named Interstate Park. They straddle the Dalles of the St. Croix River, a deep basalt gorge with glacial potholes and other rock formations. The western terminus of the Ice Age National Scenic Trail is on the Wisconsin side. In the Wisconsin side, the park is locate da bit south of St. Croix Falls, Polk County
Three state natural areas are contained within the park's 1,400 acres protecting unique glacial features and plant communities. Habitat types include upland and lowland forest, and bedrock glade. The park contains numerous wetland areas and encircles Lake O' the Dalles.
Rocks or sediment from three short intervals of geologic time, each from three different geological eras, Precambrian, Paleozoic, and Cenozoic, are exposed at the surface within Interstate Park. At least ten separate lava flows are exposed within the region of Interstate Park.
The glacial landforms and sediments of Interstate Park were largely created during the retreat of the Superior Lobe from this region and periodic outburst flood events from proglacial lakes.
It was during the regional retreat of the Lake Superior Lobe and glacial meltwater flow from deglaciation and glacial Lake Nemadji and Lake Duluth caused the entrenchment of the St. Croix River and the formation of the deep gorge of the St. Croix River of the St. Croix River valley and its famous potholes occurred.
It is exciting to see the gorge, and arguably most exciting to see the potholes. They were created starting with sand and gravel caught in eddies or whirlpools. Within the eddies, the sand and gravel were swirled around with such force that they drilled holes straight down into the rock. Larger rocks caught in the spin would polish the shafts smooth.