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Union County, New Mexico facts for kids

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Union County
Union County Courthouse in Clayton
Union County Courthouse in Clayton
Map of New Mexico highlighting Union County
Location within the U.S. state of New Mexico
Map of the United States highlighting New Mexico
New Mexico's location within the U.S.
Country  United States
State  New Mexico
Founded January 1, 1894
Seat Clayton
Largest town Clayton
 • Total 3,831 sq mi (9,920 km2)
 • Land 3,824 sq mi (9,900 km2)
 • Water 7.1 sq mi (18 km2)  0.2%%
 • Estimate 
 • Density 1.2/sq mi (0.5/km2)
Time zone UTC−7 (Mountain)
 • Summer (DST) UTC−6 (MDT)
Congressional district 3rd

Union County is the northeasternmost county in the U.S. state of New Mexico. As of the 2010 census, the population was 4,549, making it the fourth-least populous county in New Mexico. Its county seat is Clayton. The county was formed in 1894. Union County borders Colorado to the north, and Oklahoma and Texas to the east.


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. 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. At one time, Union County had a population of over 20,000. There were a number of bustling communities such as Amistad, Hayden, Sedan, Pasamonte, Gladstone, Mt Dora, Grenville, Des Moines, Folsom and Dedman (now known as Capulin).


According to the U.S. 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.

Adjacent counties

Union County is one of the few counties in the U.S. to border counties from four different states. One of its neighbors is Cimarron County, Oklahoma, the only US county to border counties from five different states.

National protected areas


Historical population
Census Pop.
1910 11,404
1920 16,680 46.3%
1930 11,036 −33.8%
1940 9,095 −17.6%
1950 7,372 −18.9%
1960 6,068 −17.7%
1970 4,925 −18.8%
1980 4,725 −4.1%
1990 4,124 −12.7%
2000 4,174 1.2%
2010 4,549 9.0%
2019 (est.) 4,059 −10.8%
U.S. Decennial Census
1790-1960 1900-1990
1990-2000 2010-2016

2010 census

As of the 2010 census, there were 4,549 people, 1,695 households, and 1,073 families living in the county. The population density was 1.2 inhabitants per square mile (0.46/km2). There were 2,305 housing units at an average density of 0.6 per square mile (0.23/km2). The racial makeup of the county was 81.7% white, 2.0% American Indian, 1.8% black or African American, 0.5% Asian, 11.7% from other races, and 2.3% from two or more races. Those of Hispanic or Latino origin made up 39.7% of the population. In terms of ancestry, 13.6% were German, 10.3% were Irish, 7.4% were English, and 7.0% were American.

Of the 1,695 households, 28.8% had children under the age of 18 living with them, 48.8% were married couples living together, 10.1% had a female householder with no husband present, 36.7% were non-families, and 33.2% of all households were made up of individuals. The average household size was 2.29 and the average family size was 2.90. The median age was 40.9 years.

The median income for a household in the county was $39,975 and the median income for a family was $41,687. Males had a median income of $29,388 versus $23,333 for females. The per capita income for the county was $19,228. About 6.9% of families and 9.8% of the population were below the poverty line, including 10.5% of those under age 18 and 9.3% of those age 65 or over.




Census-designated place

Other communities

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