The John Muir Wilderness is a wilderness area that extends along the crest of the Sierra Nevada of California for 90 miles (140 km), in the Inyo and Sierra National Forests. Established in 1964 by the Wilderness Act and named for naturalist John Muir, it encompasses 652,793 acres (2,641.76 km2). The wilderness lies along the eastern escarpment of the Sierra from near Mammoth Lakes and Devils Postpile National Monument in the north, to Cottonwood Pass near Mount Whitney in the south. The wilderness area also spans the Sierra crest north of Kings Canyon National Park, and extends on the west side of the park down to the Monarch Wilderness.