Taos and other counties in New Mexico Territory in 1852.
The southern part of present-day Colorado east of the Continental Divide was the northern part of Taos County, New Mexico Territory from its creation in New Mexico Territory in 1846 until 1861 when it was one of the four pieces of other territories used to create the new Colorado Territory.
- 22 September 1846 - Taos County was established as one of seven original New Mexico counties under Kearny's Code of Laws for the occupied Mexican territory.
- 9 January 1852 - All New Mexico counties were redefined. Taos County was extended west to the California border including land in present day Arizona and Nevada. 
- 1 February 1860 Mora County, New Mexico Territory was erected from the eastern part of Taos County including part in present-day southern Colorado.
- 28 February 1861 The northern parts of Taos and Mora counties, formerly New Mexico Territory, were transferred to the newly created Colorado Territory.
A few of the earliest settlers in what is now southern Colorado may have conducted their county business such as recording land deeds in Taos via the Santa Fe Trail. For records of residents in what later became southern Colorado, check:
Colorado eventually turned former New Mexico land into parts of these modern Colorado counties:
- Mora County became: extreme west Baca, southwest Bent, southern Custer, Huerfano, Las Animas, southern Otero, and southern Pueblo counties
- Taos County became: Alamosa, extreme southeast tip of Archuleta, Conejos, Costilla, central Hinsdale, northeast Mineral, Rio Grande, southern Saguache, and far east central San Juan counties
- ↑ 1.0 1.1 Handybook for Genealogists: United States of America, 9th ed. (Logan, Utah: Everton Pub., 1999), 274. At various libraries (WorldCat); FHL Book 973 D27e 1999.
- ↑ Kearny's Code 1846, "Courts and Judicial Powers,” secs. 5-7/p. 49; Abel, Map #2; Coan, 252; Williams, 108-109
- ↑ N.M. Terr. Laws 1851, 1st assy., 2d sess. /p. 291
- ↑ Original Counties of New Mexico Territory (map) at (accessed 9 August 2011).
- ↑ Wikipedia contributors, "Colorado Territory" in Wikipedia: the Free Encyclopeida at http://en.wikipedia.org/wiki/Colorado_Territory (accessed 19 June 2012).