Oro County, Kansas Genealogy
- Arapahoe County, Kansas Territroy (east sides of modern Adams, Arapahoe, and Elbert, and parts of Washington, Lincoln, Crowley, Otero, Bent counties in Colorado)
- Broderick County, Kansas Territory (modern Pueblo County, eastern Fremont and Custer, and southern El Paso counties, Colorado)
- El Paso County, Kansas Territory (northwestern El Paso, southern Douglas and Teller counties, Colorado)
- Fremont County, Kansas Territory (southern Park and Chaffee, Fremont, northern Custer and Saguache counties, Colorado)
- Montana County, Kansas Territory (southern Boulder, Jefferson, Gilpin, Clear Creek, Denver, northern Douglas and Park, western quarters of Arapahoe and Adams counties, Colorado)
- Oro County, Kansas Territory (central Adams, Arapahoe, and Elbert, and northwestern El Paso counties, Colorado)
When Colorado was organized 28 February 1861 its core included all parts of the original (Kansas) Arapahoe County. At that time three daughter counties were replaced, Broderick, Montana, and Oro, and their names were discontinued. The three other daughter counties, Arapahoe, El Paso, and Fremont, remained but with significantly modified borders.
For information about residents of Oro County, Kansas Territory (now in Colorado) try searching records of:
- Marshall County, Kansas
- Kansas Historical Society
- Arapahoe County, Colorado
- Colorado State Archives
- county records of the present-day Colorado county which now includes the former Oro County land where the person lived 1859-1861.
- Adrian B. Ettlinger, AniMap 3.0 : with SiteFinder U.S. place name database (Alamo, Calif.: Gold Bug, 2008), Colorado 1859 map. At various libraries (WorldCat); FHL CD-ROM no. 4903.
- "Arapahoe County, Kansas (1st) (defunct)" in Kansas Counties in Kansas Historical Society at http://www.kshs.org/geog/geog_counties/view/county:AR (accessed 25 June 2012).
- Ettlinter, Colorado 1861 map.