1872 Comprising more than 2 million acres and 10,000 hot springs, Yellowstone is established as the world’s first national park.
1903 During a trip in the Sierra with John Muir, President Theodore Roosevelt agrees to protect Yosemite Valley.
1916 The National Park Service is formed. U.S. Army officers protect its 37 sites for two years until civilian rangers take over.
1980 Alaska’s parks total 13—more than any other state—and include Wrangell–St. Elias, the country’s largest, and Denali, its highest.
2004 A national monument for 72 years, Colorado’s Great Sand Dunes gains park status, becoming number 58.
This article was first published in July 2010. Some facts may have aged gracelessly. Please call ahead to verify information.