Hartford Beach State Park sits on Big Stone Lake in a shaded native forest. Runoff from melting glaciers 10,000 years ago created the River Warren, a section of which is Big Stone Lake today. Rugged, rock-strewn bluffs and timbered shorelines surround the park. There are five hiking trails, a swimming beach, boating, fishing and disc golf. The campground has 89 campsites and four camping cabins. The park is about 15 miles north of Milbank off SD Highway 15.