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United States Nevada Carson County
Organized 17 January 1854 as part of Utah Territory. Carson County was created from the far western parts of Weber, Desert, Tooele, Juab, Millard, and Iron counties. It was enlarged in 1856, then discontinued in 1857. It was reorganized as part of Utah in 1859, but the local citizens rejected that effort. This county included all of present-day Nevada between 118° and 120° west longitude. It may also have included the Great Basin parts of eastern California.
Utah Territory's old 1856 counties are named in orange. Present-day Nevada counties are outlined in white.
Carson County was discontinued 2 March 1861 when Nevada
Territory was created. It became part of Churchill, Douglas, Esmerelda, Humboldt, Lyon, Mineral, Ormsby, Pershing, Storey, and Washoe counties, and Carson City (independent city). 
For records of Carson County, see:
- Marion Ellison, An inventory and index to the records of Carson County, Utah and Nevada Territories, 1855-1861 (Reno, Nevada : Grace Dangberg Foundation, 1984). WorldCat entry. FHL Book 979.3 R2e.