William O’Brien State Park

William O’Brien State Park, only a short drive northeast of the Twin Cities, draws large numbers of campers and daytime visitors. People are attracted by the wooded, rolling land along the St. Croix River and the variety of ways they can unwind from city life.

William O’Brien State Park is located about 2 miles north of Marine-on-St. Croix on the St. Croix Scenic Byway in Minnesota’s Washington County.

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The swimming beach at Lake Alice at William O'Brien State Park

The swimming beach at Lake Alice

A misty morning at William O'Brien State Park

A misty morning at William O’Brien State Park


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The park’s 12 miles of hiking trails include the two high points in Washington County. From one overlook, you can see Taylors Falls on a clear day. Though the park is heavily used, the trails are rarely crowded, inspiring a feeling of isolation in the wooded hills and grassy meadows.
Other trails cut through scattered stands of red and white pines, a maple-basswood forest, and the bottomlands near the river. Ancient inland seas formed the sandstone outcrops in the park. As subsequent glaciers melted, the torrent of water carved through the sandstone to form the St. Croix River Valley.
William O’Brien State Park features a paved bicycle and wheelchair path. It parallels Highway 95 the length of the park, ending in Marine-on-St. Croix.
Camping and Lodging
The park has two semi-modern campgrounds with a combined 114 sites. In the upper campground some sections are open and sunny, while others are deeply wooded. William O’Brien also has two group camping areas for a total of 85 campers.
Three year-round and one seasonal cabin have room for five to six each.
Fishing and Boating

The St. Croix River is a National Wild and Scenic River and also a state-designated canoe and boating route. The lower St. Croix, below Taylors Falls, offers easy canoeing in a pristine setting.
You can also rent canoes in William O’Brien State Park for an outing on the St. Croix River or on Lake Alice. This 15-acre lake, fed by underground springs, is stocked with panfish. Fishing on the St. Croix River can be good for walleye, northern, bass and brown trout.
Boaters and canoeists can cross Pine Slough to Greenburg Island. The island, accessible only by water, is a secluded refuge for wildlife and vegetation.

The swimming beach at Lake Alice at William O'Brien State Park

The swimming beach at Lake Alice

Swimming is not allowed in the river because of strong currents, but Lake Alice offers good swimming and a sandy beach.
The St. Croix River Valley offers visitor attractions on both sides of the river. In Minnesota, you can drive upriver to Interstate State Park or downriver to historic Stillwater. Between William O’Brien Park and Stillwater is the St. Croix Islands Scenic Reserve, where canoeists are permitted to camp on some of the islands.

Area History

The first residents of the valley were Dakota and Ojibwe. The Ojibwe eventually pushed the Dakota out of the forests to the grasslands, only to face competition from European trappers for the valley’s fur riches. In the mid 1800s, the lumberjacks who came to harvest white pine established the state’s first logging settlement at nearby Marine-on-St. Croix. You’ll find further information about the natural and human history of the park in the Sam Morgan Trail/Interpretive Center. Naturalists lead canoe floats, guided hikes and other programs during the summer.
Lake Alice is named for Alice O’Brien, who donated 180 acres of land in 1945 for the state park in memory of her father, a pioneer lumberman of the St. Croix River Valley.


12 miles of hiking trails turn into cross-country and skate ski trails during winter. Although the loops through upland fields and bottomlands are easy, the wooded hills and rolling meadows provide good skiing for intermediate and expert skiers. Whether on skis or on foot, you’ll be able to see for miles over the snowy countryside from the park’s high ridges. Snowshoeing is allowed only on Riverside Trail.
More about skiing in the Marine on St. Croix area

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