Interstate

Interstate State Park encompasses 1,330 acres along the St. Croix River at the Dalles of the St. Croix, where the river has carved a dramatic basalt gorge on the Minnesota-Wisconsin border near Taylors Falls. Established in 1900, it is Wisconsin's oldest state park. The park protects one of the most significant geological sites in the Midwest: a basalt gorge featuring the world's largest concentration of glacial potholes, some exceeding 60 feet in depth, drilled into billion-year-old lava flows by the swirling glacial meltwater floods at the end of the last Ice Age.

The park's river gorge and surrounding forests support diverse wildlife. White-tailed deer, foxes, raccoons, and numerous small mammals inhabit the forest. The St. Croix River supports smallmouth bass, walleye, channel catfish, and other warm-water fish species. The river corridor is an important flyway for migratory birds, with warblers, vireos, and thrushes passing through in spring and fall. Bald eagles fish along the river year-round. Turkey vultures soar on thermals above the gorge. The park's rock outcrops provide habitat for specialized plants and animals adapted to cliff environments.

The park's vegetation reflects its position at the junction of prairie, northern hardwood, and boreal forest influences. White pine and red pine grow on the rocky bluffs above the gorge. Northern hardwood forest of sugar maple, basswood, and red oak covers the uplands. The steep, south-facing slopes of the gorge support remnant prairie plant communities including big bluestem and little bluestem grasses. The moist gorge floor supports ferns, mosses, and shade-tolerant wildflowers. The rock surfaces in the Dalles support lichens and mosses adapted to the exposed volcanic substrate.

The Dalles of the St. Croix feature spectacular exposures of 1.1-billion-year-old basalt lava flows from the Midcontinent Rift, the same volcanic episode that created the Porcupine Mountains and the Lake Superior basin. These ancient lava flows have been carved into a narrow gorge by the St. Croix River. The park's glacial potholes were drilled into the basalt during catastrophic floods from Glacial Lake Duluth approximately 10,000 years ago, when enormous volumes of meltwater funneled through the gorge. The largest potholes are cylindrical holes over 60 feet deep and 10 feet in diameter, created by rocks spinning in powerful vortices within the floodwaters.

The park experiences a humid continental climate with warm summers and cold winters. Summer temperatures reach the upper 70s to mid-80s Fahrenheit. Winters are cold, with temperatures frequently well below zero and moderate snowfall. The river gorge creates a cooler microclimate in summer and can trap cold air in winter. Annual precipitation averages about 32 inches. The St. Croix River generally freezes in winter, though the gorge section may retain open water longer due to water turbulence. Spring ice-out on the river can be dramatic.

The St. Croix River valley has been inhabited by indigenous peoples for thousands of years. The Ojibwe and Dakota peoples used the river as a travel corridor and fishing resource. The Dalles area held cultural significance as a notable geographic feature. European-American exploration and the fur trade brought French voyageurs to the river in the 1600s and 1700s. The timber industry dominated the region in the mid-to-late 1800s, with massive log drives floating timber down the St. Croix through the narrow Dalles. The geological significance of the Dalles was recognized early by scientists, leading to conservation efforts.

Interstate State Park was established in 1900 as Wisconsin's first state park, and its Minnesota counterpart across the river was established the same year. The parks were created primarily to protect the unique geological features of the Dalles from quarrying and development. The St. Croix River gorge had attracted scientific attention throughout the 1800s for its remarkable glacial potholes and exposed ancient volcanic rocks. The park's establishment represented an early recognition that significant natural features deserved permanent protection for public enjoyment and scientific study.

The Pothole Trail winds among the park's remarkable glacial potholes, the world's largest concentration, with interpretive signs explaining their formation. The Lake o' the Dalles and Horizon Rock Trail provides dramatic views of the river gorge and basalt cliffs. The Bluff Trail and Echo Canyon Trail explore the rugged gorge topography. River excursion boats offer narrated tours through the Dalles during summer months, providing water-level views of the gorge and its geological features. Rock climbing is popular on designated cliff faces. Cross-country skiing and snowshoeing provide winter recreation on the park's trails.

The park offers 85 campsites in two campground areas, with some sites offering electric hookups. A nature center provides geological and natural history exhibits. The park beach on Lake o' the Dalles provides swimming. Picnic areas, shelters, and a concession stand serve day visitors. The park is located on Highway 35 in St. Croix Falls, Wisconsin, approximately 50 miles northeast of Minneapolis-St. Paul. The Twin Cities metro area provides major airport service and extensive lodging. Taylors Falls, Minnesota, directly across the river, offers additional dining and lodging options. A vehicle admission sticker is required.

The St. Croix River's designation as a National Scenic Riverway provides broader protection for the river ecosystem that flows through the park. Water quality monitoring ensures the river remains healthy for recreation and aquatic life. The park's geological features require protection from visitor impacts including climbing on and removing rock from the fragile pothole formations. Invasive species management addresses threats from garlic mustard, buckthorn, and emerald ash borer. The park collaborates with Minnesota's Interstate State Park across the river for coordinated management of the shared Dalles landscape.