New Mexico Counties
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New Mexico Counties

There is thirty-three counties in the state of New Mexico. 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.

Union County, New Mexico

Union County Education, Geography, and HistoryUnion County, New Mexico Courthouse

Union County is the northernmost county in the state of New Mexico. Based on the 2010 census, the population was 4,549, making it the fourth-least populous county in New Mexico. Union County, was created by an act of the territorial legislation in 1893 and was officially recognized on January 1, 1894, when the first slate of elected county officials received their oaths of office. Union County borders Colorado to the north, and Oklahoma and Texas to the east. The county is named 'Union' because the citizens were united in their desire for the creation of a new county out of three existing New Mexico counties. Union County was subsequently 'carved up' by the creation of additional counties, Quay in 1903 and Harding in 1920. Its county seat is Clayton. 

Etymology - Origin of Union County Name

Union County was formed from parts of Colfax, Mora, and San Miguel Counties.  Union was named for the "union" of the counties mentioned.


County QuickFacts: CensusBureau Quick Facts

Union County History

Union County was created 13 February 1893. The county seat is Clayton. Union County was formed from parts of Colfax, Mora, and San Miguel Counties. Researchers might check these related counties for resources. Union was named for the "union" of the counties mentioned. The old Santa Fe Trail traverses Union County. The famous Goodnight-Loving Cattle Drive Trail also crosses Union County. The area is as beautiful as the other Northeast New Mexico Counties.

Geography: Land and Water

As reported by the Census Bureau, the county has a total area of 3,831 square miles (9,920 km2), of which 3,824 square miles (9,900 km2) is land and 7.1 square miles (18 km2) (0.2%) is water.

Neighboring Counties

Bordering counties are as follows:

  • Las Animas County, Colorado (north)
  • Baca County, Colorado (northeast)
  • Cimarron County, Oklahoma (east)
  • Dallam County, Texas (east)
  • Hartley County, Texas (southeast)
  • Quay County (south)
  • Harding County (south)
  • Colfax County (west)


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