White River National Forest is a National Forest in northwest Colorado. It is named after the White River that passes through the forest. It also contains the Flat Tops Wilderness Area, largely considered the birthplace of the U.S. Wilderness Area system. The Aspen and Vail ski resorts are located inside the forest, as are the Maroon Bells, a famous collection of Paleozoic sandstone and mudstone peaks near Aspen. The forest contains 2,285,970 acres (3,571.8 sq mi, or 9,250.99 km²).