|NM State Facts|
|Territory: Sep 9, 1850|
|Statehood: Jan 6, 1912|
|Borders: AZ, CO, OK, TX and UT|
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Today’s New Mexico counties did not always exist in the present form. They went through many different changes in the space of a few short years.
New Mexico Territorial Counties
The New Mexico Territory was organized as territory on September 9, 1850. There were originally nine counties formed in 1852. Santa Ana County, New Mexico Territory, one of the nine original counties, was annexed in 1876 to Bernalillo County, New Mexico.
The State of New Mexico entered the union as the 47th state on January 6, 1912.
New Mexico Counties Today
Fun Facts about New Mexico Counties
Counties by Year
- Socorro, San Miguel, Taos, Rio Arriba, Valencia, Santa Fe, Doña Ana and Bernalillo Counties was the original 9 counties created in 1852.
- Cibola County was the last county created on 1981.
County Size Facts
- Catron County (6,928 sq mi) is the largest county in New Mexico.
- Los Alamos County (109 sq mi) is the smallest county in New Mexico.
County Population Facts
- Harding County (740) is the least populated county in New Mexico.
- Bernalillo County (670,968) is the most populated county in New Mexico.
New Mexico City Facts
New Mexico’s 10 largest cities (2016 est.) are:
- Albuquerque (545,852) is in Bernalillo County
- Las Cruces (97,618) is in Doña Ana County
- Rio Rancho (87,521) is in Bernalillo County and Sandoval County
- Santa Fe (67,947) is in Santa Fe County
- Roswell (48,366) is in Chaves County
- Farmington (45,877) is in San Juan County
- Clovis (37,775) is in Curry County
- Hobbs (34,122) is in Lea County
- Alamogordo (30,403) is in Otero County
- Carlsbad (26,138) is in Eddy County
Boundary Changes of New Mexico Counties from 1845-1981
This Interactive Map of New Mexico Counties show the historical boundaries, names, organization, and attachments of every county, extinct county and unsuccessful county proposal from 1845 to 1981.
List of New Mexico Counties
|County||Date Formed||Parent County||County Seat|
|Bernalillo||1852||One of the nine original counties.||Albuquerque|
|Catron||1921||Part of Socorro County.||Reserve|
|Chaves||1889||Part of Lincoln County.||Roswell|
|Cibola||1981||Part of Valencia County.||Grants|
|Colfax||1869||Part of Mora County.||Raton|
|Curry||1909||Parts of Quay and Roosevelt Counties.||Clovis|
|De Baca||1917||Parts of Chaves and Guadalupe Counties.||Fort Sumner|
|Dona Ana||1852||One of the nine original counties.||Las Cruces|
|Eddy||1889||Part of Lincoln County.||Carlsbad|
|Grant||1868||Part of DoÃ±a Ana County.||Silver City|
|Guadalupe||1891||Part of San Miguel County.||Santa Rosa|
|Harding||1921||Parts of Mora and Union Counties.||Mosquero|
|Hidalgo||1919||Part of Grant County.||Lordsburg|
|Lea||1917||Parts of Chaves and Eddy Counties.||Lovington|
|Lincoln||1869||Part of Socorro County.||Carrizozo|
|Los Alamos||1949||Parts of Sandoval and Santa Fe Counties.||Los Alamos|
|Luna||1901||Parts of DoÃ±a Ana and Grant Counties.||Deming|
|McKinley||1899||Part of Bernalillo County.||Gallup|
|Mora||1860||Part of Taos County.||Mora|
|Otero||1899||Parts of DoÃ±a Ana and Lincoln Counties.||Alamogordo|
|Quay||1903||Part of Guadalupe County.||Tucumcari|
|Rio Arriba||1852||One of the nine original counties.||Tierra Amarilla|
|Roosevelt||1903||Parts of Chaves and Guadalupe Counties.||Portales|
|San Juan||1887||Part of Bernalillo County.||Bernalillo|
|San Miguel||1852||Part of Rio Arriba County.||Aztec|
|Sandoval||1903||One of the nine original counties.||Las Vegas|
|Santa Fe||1852||One of the nine original counties.||Santa Fe|
|Sierra||1884||Parts of DoÃ±a Ana and Socorro Counties.||Truth or Consequences|
|Socorro||1852||One of the nine original counties.||Socorro|
|Taos||1852||One of the nine original counties.||Taos|
|Torrance||1903||Parts of Bernalillo and Valencia Counties.||Estancia|
|Union||1893||Parts of Colfax, Mora and San Miguel Counties.||Clayton|
|Valencia||1852||One of the nine original counties.||Los Lunas|
List of Old Former / Extinct New Mexico Counties
New Mexico contains some counties that no longer exist because they were discontinued, renamed or merged with another county. These are important for genealogy research purposes.
The below counties formerly within the area of the State of New Mexico no longer exist:
Santa Ana County, New Mexico
[1852 Map] was one of the seven original partidos created in New Mexico under Mexican rule (was in Judicial District No. 1 from 1847 to 1863, then in JD 2 until 1876). Under U.S. rule, it became a U.S. Territorial county from 1852 until 1876, when it was absorbed by Bernalillo County.