Forest Park stretches through the Tualatin Mountains just west of downtown Portland as one of the largest urban forest reserves in the United States. More than eight miles long and covering over 5,100 acres, it contains more than eighty miles of trails and was created through a long effort to preserve the wooded hills above the Willamette River, culminating in its formal dedication in 1948. Though close to the city center, it functions as a substantial ecosystem of mostly second-growth forest, streams, and wildlife habitat. Its steep basalt and silt slopes shape both its scenic views and its vulnerability to erosion, landslides, invasive plants, and heavy urban use.