Plan an extended visit to St. Croix. With over 34,000 acres and two great rivers: the Saint Croix River, a National Scenic Riverway, and the Kettle River, a State Wild and Scenic River, there's so much to do. Explore the rivers by canoe or with a fishing pole. Swim at Lake Clayton or climb a fire tower. The park has miles of trails for hikers, horseback riders, bicyclists, snowmobilers, and cross-country skiers. Campers can reserve drive-in, walk-in, backpack, and horseback campsites. Large groups can reserve the modern group centers or the primitive group camps.

Twenty-one miles of the St. Croix River, a National Scenic Riverway, form the eastern boundary of the park, while Minnesota's first Wild and Scenic River, the Kettle River, joins the St. Croix to form the western boundary. At least ten other streams flow through the park, creating a watershed of hundreds of square miles. These waterbodies also provide important opportunities for canoeing, fishing, and kayaking. St. Croix State Park, which is on the eastern edge of the Mille Lacs Uplands, is an important site for plants and animals too. Once home to stands of virgin red and white pine, today, St. Croix State Park is a mix of natural communities including a unique plant community called the jackpine barrens. Visitors will see areas where work is being done to reintroduce fire into the jack pine to promote restoration of this ecosystem. An enormous diversity of plants and animals are common, including the stemless lady-slipper or moccasin flower, blazing stars, bald eagles, black bears, and timber wolves.

During the last glacial period, about 10,000 years ago, the St. Croix River valley served as a major drainage channel for glacial meltwater from Lake Superior. As these waters carved the way for the river seen today, the waters left behind a variety of soils and sediment that cover the ancient lava bedrock far below, including a glacial outwash plain of sand left by Glacial Lake Grantsburg. Many springs along the river banks occur where the river valley has eroded through the glacial gravel to release water trapped between the sediments. The final wave of glacial meltwater cleaned debris from the Kettle River valley, leaving much of the basalt and sandstone bedrock exposed. A stop at the Kettle River Highbanks is a step back over millions of years.

The habitats consist of both aspen and conifers, which benefits wildlife including black bear, coyotes, beaver, raccoons, gray and red fox, and deer. Eastern timber wolves are also found in the park but are not commonly seen. Many species of birds thrive here: warblers, flycatchers, eagles, owls, and osprey are common along the St. Croix.

The St. Croix River was an important trade route for hundreds of years, first for the Native Americans, and then for the French, English, and American fur traders. Although the fur trade ended during the mid 1800's, logging camps along the St. Croix River sprung up, all taking advantage of the river's force to float logs to lumber mills downstream. By 1915, the logging era had moved on to other parts of the country. The newly cleared land was attractive to farmers and immigrants from all over the world, but these settlers struggled to make a living from the poor soil. In 1934, 18,000 acres of St. Croix area farmland was purchased, and in 1935, became the St. Croix Recreational Demonstration Area. Under the direction of the National Park Service, the Civilian Conservation Corps (CCC) and the Works Progress Administration (WPA), set out to transform these lands into group camps, roads, and campgrounds, with all the necessary buildings and structures. Most of their efforts remain in use today, with many of the buildings and structures listed on the National Register of Historic Sites. Interpretive signs throughout the former CCC campsite describe the lives and work of the CCC's in the St. Croix RDA, which in 1943, became St. Croix State Park.