Walnut Woods State Park is a 250-acre preserve in West Des Moines, Iowa, centered on a bottomland hardwood forest along the Raccoon River. It protects the largest natural stand of black walnut trees in North America, giving the park unusual ecological importance. The river shapes the landscape and supports activities such as fishing and canoeing, while picnic areas and a small campground make it both a day-use and overnight destination near the city. A limestone lodge from the 1930s adds historic character, and the park is also known for its wildlife, including more than 90 recorded bird species.