Rio Virgin (or Rio Virgen) was a former county of Utah Territory from 1869 to 1872. It was created by Utah, but only a small bit of Rio Virgin county was actually in the territory. It mostly covered land outside of Utah in Nevada and Arizona, which also lay claim to the land. 
- 18 January 1867 - The US federal government transferred the northwest corner of Arizona Territory to Nevada.  Nevada used the land to increase Lincoln County and Nye County. Arizona opposed loosing this land, twice petitioned Congress for repeal of the law. Utah also opposed this transfer of land
- 18 February 1869 - Utah created Rio Virgin County. It was meant to serve the residents of Mesquite, St. Thomas, Bunkerville and other nearby towns which Utah wanted to keep within its influence. The US federal government surveyed the land, which showed Rio Virgin County was mostly in Nevada, with some in Pah-Ute County, Arizona and a small part in Utah.
- 16 February 1872 - Utah discontinued Rio Virgin County, finally accepting the transfer after exhausting all legal remedies.  The tiny bit of Rio Virgin County actually in Utah was restored to Washington County.
Records for Rio Virgin County, Utah Territory may be found:
- Utah State Archives may have a few records from the Utah Territory's Rio Virgin County courts and deeds.
- Death Record Substitutes
- 1870 - U.S. Federal Census Mortality Schedules, 1850-1885 at Ancestry ($). Includes 1870 Rio Virgin County, Utah Genealogy mortality schedule.
- Previous Jurisdictions to Land in Arizona showing dates the jurisdictions were created and maps. This will help in determining what jurisdiction your ancestor lived in and where the records are now located.
- ↑ Handybook for Genealogists: United States of America, 10th ed. (Draper, Utah: Everton Pub., 2002), 687. At various libraries (WorldCat). FHL Book 973 D274 2002.
- ↑ 2.0 2.1 "Chart of County Formation in Utah" in Division of Archives and Records Service at http://archives.utah.gov/research/guides/county-formation.htm (accessed 11 August 2011).
- ↑ U.S. Stat., vol. 14, ch. 73/p. 43; Sacks, 25; Van Zandt, p. 158, 165
- ↑ Utah Terr. Laws 1869, 18th session, ch. 10, p. 7
- ↑ Deon C. Greer, Atlas of Utah (Ogden, Utah: Utah State College, 1981), 162 and 164. At various libraries (WorldCat). FHL Q Book 979.2 E7a.
- ↑ Utah Terr. Laws 1872, 20th session, ch. 19, sec. 2, p. 28
- ↑ Greer, 162