County Maps US

Union County, New Mexico

A county in New Mexico, ranked 30 of 33 by population.

CountyFIPS 35059

Within New Mexico
Union County, highlighted, with the areas around it. Boundaries generalised from the 2025 Census cartographic boundary file; neighbour fills carry no data. The dot marks Clayton, the county seat, located via the 2025 Census Gazetteer.

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Population
3,844
-226 (-5.6%) since 2020
Land area
3,825
square miles. A further 0.2% of the total area is water
Population density
1.0
people per square mile, computed rather than published
County seat
Clayton
Seat of county government.
Established
1894
131 years ago
Largest city
Clayton town
Population 2,510.

Sources: US Census Bureau, Population Estimates Program, Vintage 2025 Population Estimates, released 26 March 2026; US Census Bureau, Gazetteer Files, 2025 Gazetteer Files, released 10 September 2025; Wikidata (CC0), Wikidata. Retrieved 30 August 2026.

Satellite view

Aerial imagery of Union County with its boundary drawn on top. A map shows you the shape; this shows you what is inside it, and which side of the line a place falls on.

Aerial view of Union County, New Mexico from the USGS National Map, with its boundary outlined
Imagery: USGS National Map, USGS Imagery Only, public domain, requested from USGS by your browser when you reach this point on the page, at 545 by 800 pixels. The boundary is the 2025 Census cartographic boundary file, reprojected to Web Mercator to match the imagery. You can also open the USGS National Map viewer.

Where Union County ranks

Position among the 33 counties of New Mexico, and among all 3,144 US counties and county-equivalents. Computed from the figures on this page.

MeasureValueIn New MexicoNationally
Population3,84430th of 332,894th of 3,144
Land area3,825 sq mi15th of 33129th of 3,144
Population density1.0 per sq mi30th of 333,072nd of 3,144
Median household income$46,69426th of 322,910th of 3,143

Full data for Union County

Every figure below is attributed to the Census Bureau product it came from, with the vintage of that product.
MeasureValueSource and vintage
Population3,844Vintage 2025 Population Estimates
Population in 20204,070Vintage 2025 Population Estimates
2020 estimates base?4,082Vintage 2025 Population Estimates
Land area3,825 sq mi2025 Gazetteer Files
Water area6.0 sq mi2025 Gazetteer Files
Total area3,831 sq mi2025 Gazetteer Files
Population density?1.0 per sq miComputed: Vintage 2025 estimates divided by 2025 Gazetteer land area
Median household income$46,694American Community Survey 2020-2024 5-Year Estimates
Median home value$122,700American Community Survey 2020-2024 5-Year Estimates
Median age42.6American Community Survey 2020-2024 5-Year Estimates
Households1,438American Community Survey 2020-2024 5-Year Estimates
Housing units2,101American Community Survey 2020-2024 5-Year Estimates

Sources: US Census Bureau, Population Estimates Program, Vintage 2025 Population Estimates, released 26 March 2026; US Census Bureau, Gazetteer Files, 2025 Gazetteer Files, released 10 September 2025; US Census Bureau, American Community Survey, American Community Survey 2020-2024 5-Year Estimates, released 29 January 2026. Population density is computed here, not published: it divides the Vintage 2025 population estimate by the 2025 Gazetteer land area, which are two different Census products. Retrieved 30 August 2026.

How the population changed

The Census Bureau publishes the components behind an estimate, not just the total. For the year to July 2025:

Births minus deaths
-26
31 births, 57 deaths
Net migration
-70
More people moved out than moved in.

Source: US Census Bureau, Population Estimates Program, Vintage 2025 Population Estimates, released 26 March 2026. Retrieved 30 August 2026.

The 8 areas bordering Union County

Ordered by the length of the border actually shared, which the Census Bureau publishes in its county adjacency file and which no other county reference presents.

Bordering areaStateShared borderPopulation
Harding CountyNew Mexico70 mi617
Colfax CountyNew Mexico54 mi12,184
Las Animas CountyColorado51 mi14,391
Cimarron CountyOklahoma34 mi2,059
Dallam CountyTexas33 mi7,508
Hartley CountyTexas22 mi4,904
Quay CountyNew Mexico19 mi8,454
Baca CountyColorado4.6 mi3,347

Source: US Census Bureau, County Adjacency File, 2025 County Adjacency File, released 15 September 2025. Retrieved 30 August 2026.

All 33 counties of New Mexico

Open the interactive New Mexico county map, or jump straight to any of them.

Data on this page last rebuilt 30 August 2026. How these figures are produced.