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Frederick Law Olmstead pushes for protection of Yosemite Valley and is first to advance the idea of placing certain areas under government protection.
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African American fur trapper and explorer James P. Beckwourth finds an important route through the Sierra Nevadas, leading the first wagon train of settlers through what would become "Beckwourth Pass."
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Transcendentalist Henry David Thoreau, author of Walden, writes that wilderness sanctuaries are the "need of civilized man."
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Artist Thomas A. Ayers' lithographs introduce Yosemite to the East. Country Gentleman republishes articles that declare the Yosemite Valley to be "the most striking natural wonder on the Pacific."
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Photographs by Carleton E. Watkins make Yosemite Valley famous.
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The Alaska Purchase is signed by President Andrew Johnson, adding 365 million acres of public lands to the United States.
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Surveyors, escorted by the 7th U.S. Cavalry under the command of Lieutenant George A. Custer, penetrate the Black Hills of South Dakota, an area considered sacred by the Sioux tribes.
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Battle of the Little Bighorn occurs in Montana on what is now the Little Bighorn Battlefield National Monument.
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Casa Grande Ruins N.M. becomes the first prehistoric cultural site to be protected by the federal government.
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Gifford Pinchot takes office as Chief of the Division of Forestry, later organized into the National Forest Service in 1905, advancing conservation of natural resources.