John Muir wrote more than 300 magazine articles and 10 major books and was still writing when he died. It is estimated he left enough material for 10 more books. Muir's works are in numerous collections. A major collection is held by the Holt-Atherton Department of Special Collections, University of the Pacific, Stockton.

Muir not only knew the western wilderness well, he spent a large part of his life fighting tirelessly for its preservation. He met powerful Americans of the late 19th and early 20th Century to enlist their help. He brought President Theodore Roosevelt and many others to Yosemite. His interests ranged to many aspects of science and nature.
He was actively involved in the creation of several National Parks and supported the creation of a National Park System.