The Oregon Dunes National Recreation Area is located on the Oregon Coast, stretching approximately 40 miles north from the Coos River in North Bend, to the Siuslaw River, in Florence. The Recreation Area is part of Siuslaw National Forest and is administered by the United States Forest Service. The Oregon Dunes are a unique area of windswept sand that is the result of millions of years of wind and rain erosion on the Oregon Coast. These are the largest expanse of coastal sand dunes in North America. Some dunes tower up to 500 feet above sea level.