|Counties of New Mexico|
|Location||State of New Mexico|
|Populations||639 (Harding) – 674,393 (Bernalillo)|
|Areas||109 square miles (280 km2) (Los Alamos) – 6,928 square miles (17,940 km2) (Catron)|
The New Mexico Territory was organized in September 1850. The first nine counties in the territory to be created, in 1852, were Bernalillo, Doña Ana, Rio Arriba, San Miguel, Santa Ana, Santa Fe, Socorro, Taos, and Valencia Counties. Mora County was created in 1860. Following the Gadsden Purchase of 1853–1854, the northeasternmost part of the New Mexico Territory was ceded to the new Colorado Territory in February 1861, before the western half was reorganized as the Arizona Territory in February 1863, establishing New Mexico's present-day boundaries.
Grant County was created in 1868, followed by Colfax and Lincoln Counties in 1869. In 1876, Santa Ana County was absorbed by Bernalillo County. A further 14 counties were then created between 1884 and 1909, bringing the total number to 26.
New Mexico was admitted to the Union as the 47th state on January 6, 1912. De Baca and Lea Counties were created in 1917, followed by Hidalgo County in 1920 and Catron and Harding Counties in 1921. Los Alamos County was created in 1949 and finally Cibola County in 1981, bringing the total number of counties to 33.
The Federal Information Processing Standard (FIPS) code, which is used by the United States government to uniquely identify states and counties, is provided with each entry. New Mexico's code is 35, which when combined with any county code would be written as 35XXX. The FIPS code for each county links to census data for that county.
For comparison, the population estimate for the state of New Mexico as of July 2011 was 2,082,224, and the area was 121,589 mi2 (315,194 km2).
|Bernalillo County||001||Albuquerque||1852||One of the nine original counties.||The Gonzales-Bernal family, Spanish nobles who settled the territory in the seventeenth century||674,393||1,166 sq mi
|Catron County||003||Reserve||1921||Part of Socorro County.||Thomas Benton Catron (1840-1921), a Santa Fe attorney and New Mexico's first U.S. Senator||3,731||6,928 sq mi
|Chaves County||005||Roswell||1889||Part of Lincoln County.||Jose Francisco Chaves (1833-1904), a U.S. Army colonel in New Mexico during and after the Civil War||64,629||6,071 sq mi
|Cibola County||006||Grants||1981||Parts of Valencia County, Socorro County, McKinley County, and Catron County.||The mythical Seven Cities of Cibola||27,184||4,540 sq mi
|Colfax County||007||Raton||1869||Part of Mora County.||Schuyler Colfax (1823-1885), the seventeenth vice president of the United States||12,369||3,757 sq mi
|Curry County||009||Clovis||1909||Parts of Quay County and Roosevelt County.||George Curry (1861-1947), a governor of New Mexico Territory from 1907 to 1910||47,999||1,406 sq mi
|De Baca County||011||Fort Sumner||1917||Parts of Chaves County and Guadalupe County.||Ezequiel Cabeza de Baca (1864-1917), the second state governor of New Mexico||1,680||2,325 sq mi
|Doña Ana County||013||Las Cruces||1852||One of the nine original counties.||Doña Ana Robledo, a seventeenth-century Spanish woman known for her charitable giving to the native population||221,508||3,807 sq mi
|Eddy County||015||Carlsbad||1887||Part of Lincoln County.||Charles Eddy (1857 - 1931), a rancher and developer of the area||60,911||4,182 sq mi
|Grant County||017||Silver City||1868||Part of Doña Ana County.||Ulysses Simpson Grant (1822-1885), the Civil War general and eighteenth president of the United States||27,889||3,966 sq mi
|Guadalupe County||019||Santa Rosa||1891||Part of San Miguel County.||Our Lady of Guadalupe, the patron saint of the Americas||4,449||3,031 sq mi
|Harding County||021||Mosquero||1921||Parts of Mora County and Union County.||Warren Gamaliel Harding (1865-1923), the twenty-ninth president of the United States||639||2,126 sq mi
|Hidalgo County||023||Lordsburg||1920||Part of Grant County.||The Treaty of Guadalupe Hidalgo, named after a Mexican town in turn named for Miguel Hidalgo y Costilla (1753 - 1811), the priest who is known as the Father of Mexican Independence||4,074||3,446 sq mi
|Lea County||025||Lovington||1917||Parts of Chaves County and Eddy County.||Joseph Calloway Lea (1841-1904), a captain in the U.S. Army and the founder of the New Mexico Military Academy||73,004||4,393 sq mi
|Lincoln County||027||Carrizozo||1869||Part of Socorro County.||Abraham Lincoln (1809-1865), the sixteenth president of the United States||20,436||4,831 sq mi
|Los Alamos County||028||Los Alamos||1949||Parts of Sandoval County and Santa Fe County.||Named for its county seat of Los Alamos, New Mexico, which itself is the Spanish name for the cottonwood tree||19,330||109 sq mi
|Luna County||029||Deming||1901||Parts of Doña Ana County and Grant County.||Solomon Luna (1858 - 1912), the largest land owner in the county at the time of its creation; itself Spanish for moon||25,532||2,965 sq mi
|McKinley County||031||Gallup||1899||Part of Bernalillo County.||William McKinley (1843-1901), the twenty-fifth president of the United States||71,780||5,449 sq mi
|Mora County||033||Mora||1860||Part of Taos County.||Named for its county seat of Mora, New Mexico, which is itself named after lo de mora, the Spanish term for blackberry||4,196||1,931 sq mi
|Otero County||035||Alamogordo||1899||Parts of Doña Ana County and Lincoln County.||Miguel A. Otero (1829-1882), territorial delegate to U. S. Congress or Miguel Antonio Otero (II) (1859-1944), 16th Governor of New Mexico Territory from 1897 to 1906||68,537||6,627 sq mi
|Quay County||037||Tucumcari||1903||Part of Guadalupe County.||Matthew Stanley Quay (1833-1904), a U.S. Senator from Pennsylvania who supported New Mexico's statehood||8,656||2,855 sq mi
|Rio Arriba County||039||Tierra Amarilla||1852||One of the nine original counties.||Named for its location on the upper Rio Grande (Río Arriba means "upstream" or "up the river" in Spanish)||40,179||5,858 sq mi
|Roosevelt County||041||Portales||1903||Parts of Chaves County and Guadalupe County.||Theodore Roosevelt (1858-1919), the twenty-sixth president of the United States||19,019||2,449 sq mi
|Sandoval County||043||Bernalillo||1903||Part of Bernalillo County.||Named for the Sandoval family, prominent seventeenth-century Spanish landowners||151,369||3,710 sq mi
|San Juan County||045||Aztec||1887||Part of Rio Arriba County.||San Juan River, itself named after the Catholic saint||120,993||5,514 sq mi
|San Miguel County||047||Las Vegas||1852||One of the nine original counties.||San Miguel de Bado Catholic Church, the first in the area||27,150||4,717 sq mi
|Santa Fe County||049||Santa Fe||1852||One of the nine original counties.||Named after the city of Santa Fe whose full Spanish name is “La Villa Real de la Santa Fe de San Francisco de Assisi” or “The royal city of the holy faith of St. Francis of Assisi”||155,201||1,909 sq mi
|Sierra County||051||Truth or Consequences||1884||Parts of Doña Ana County and Socorro County.||Possibly named for the Black Range. (Sierra is mountain range in Spanish.)||11,502||4,180 sq mi
|Socorro County||053||Socorro||1852||One of the nine original counties.||Spanish term meaning "aid," which refers to the help Native Americans gave to starving travelers||16,311||6,647 sq mi
|Taos County||055||Taos||1852||One of the nine original counties.||Named for its county seat of Taos, New Mexico, which in turn was named for the nearby Taos Pueblo, an ancient Native American village. Taos is red willow in the Tiwa language||34,623||2,203 sq mi
|Torrance County||057||Estancia||1903||Parts of Bernalillo County, Valencia County, and Socorro County.||Francis J. Torrance (1859 - 1919), the developer of the New Mexico Central Railroad||15,307||3,345 sq mi
|Union County||059||Clayton||1893||Parts of Colfax County, Mora County and San Miguel County.||Named for the "union" of the three counties which donated land to form the new county||4,107||3,830 sq mi
|Valencia County||061||Los Lunas||1852||One of the nine original counties.||Named for the town of Valencia, New Mexico, which is itself named for Valencia, Spain||77,190||1,068 sq mi
- Arizona County, New Mexico Territory, is mentioned in the 1860 United States Census.
- Mesilla County, appears on 1860s-era territorial map encompassing area in present-day Dona Aña, Grant, Hidalgo, Luna, Sierra west of the Rio Grande
- Santa Ana County (1844–1876) absorbed by Bernalillo County; portions are in present-day McKinley County
- Santa Fe County, Texas (1848-1850), never organized, included the portion of New Mexico east of the Rio Grande except for southeastern New Mexico east of the Pecos River and south of the Prairie Dog Town Fork Red River as well as the Trans-Pecos and most of the Panhandle regions of Texas, the Oklahoma Panhandle, and portions of Colorado, Kansas, and Wyoming. Before Texas ceded its western lands to the federal government after the Compromise of 1850, the following counties were briefly created from Santa Fe County earlier that year in south-central New Mexico between the Rio Grande and the Pecos:
- "FIPS Publish 6-4". National Institute of Standards and Technology. Archived from the original on September 29, 2013. Retrieved August 6, 2007.
- "EPA County FIPS Code Listing". US Environmental Protection Agency. Retrieved 2007-08-06.
- "NACo - Find a county". National Association of Counties. Archived from the original on 2007-09-30. Retrieved 2007-08-07.
- "NMGenWeb Counties". Rootsweb.com. Archived from the original on 2007-07-02. Retrieved 2007-08-06.
- Viva New Mexico County Names Archived 2008-07-04 at the Wayback Machine
- "U.S. Census Bureau QuickFacts: New Mexico". U.S. Census Bureau. Retrieved March 31, 2022.
- "New Mexico QuickFacts". U.S. Census Bureau. Archived from the original on 2011-12-27. Retrieved 2007-08-07. (2000 Census)
- https://www2.census.gov/library/publications/decennial/1860/population/1860a-42.pdf[bare URL PDF]