Biographer Steven J. Holmes once wrote that John Muir was "one of the patron saints of twentieth-century American environmental activity." In his lifetime, the engineer, author, biologist, and activist worked alongside powerful men such as President Theodore Roosevelt, railroad executive E. H. Harriman, and conservationist Gifford Pinchot. Muir was responsible for the creation of the Sierra Club and he played an important role in preserving the Yosemite Valley and Sequoia National Park.