Yosemite National Park Pass Ski Area—the oldest downhill skiing area in California, offering downhill skiing from mid-December through early April. Much of the park is open to cross-country skiing and snowshoeing, with several backcountry ski huts open for use. Wilderness permits are required for backcountry overnight ski trips. The Bracebridge dinner is an annual holiday event, held since 1927 at the Ahwahnee Hotel, inspired by Washington Irving's descriptions of Squire Bracebridge and English Christmas traditions of the 18th century in his "Sketch Book". Between 1929 and 1973, the show was organized by Ansel Adams. Bicycle rentals are available in Yosemite Valley spring through
Yosemite National Park alpine glaciers, bucking established scientists such as Josiah Whitney, who regarded Muir as an amateur. Muir wrote scientific papers on the area's biology. Landscape architect Frederick Law Olmsted emphasized the importance of conservation of Yosemite Valley. Overgrazing of meadows (especially by sheep), logging of giant sequoia, and other damage caused Muir to become an advocate for further protection. Muir convinced prominent guests of the importance of putting the area under federal protection; one such guest was Robert Underwood Johnson, editor of "Century Magazine". Muir and Johnson lobbied Congress for the Act that created Yosemite National Park on October 1, 1890.