County facts · Land area · October 21, 2026

Largest Counties in New Mexico by Area and Population

The largest New Mexico counties by land area and by 2023 population, plus the smallest, county seats and a link to each official parcel map.

Looking for the largest counties in New Mexico? New Mexico has 33 counties covering about 121,313 square miles of land, based on the Census Bureau's 2020 Gazetteer. The largest by land area is Catron County, at about 6,924 square miles, roughly 63 times the size of the smallest, Los Alamos County (109 sq mi). Measured by people instead, the largest is Bernalillo County, with about 671,586 residents in the Census Bureau's July 1, 2023 estimate.

Each table below links the county's Platbookmapper page and its official parcel viewer, so you can go straight from the numbers to the property lines.

New Mexico counties at a glance

• Counties: 33
• Land area: about 121,313 sq mi, plus about 280 sq mi of water inside county lines
• Residents, 2023 estimates: about 2,114,371, or about 17 people per square mile of land
• Median county land area: about 3,758 sq mi
• With a verified public parcel viewer in our directory: 33 of 33 (30 of them through a statewide viewer)

The 10 largest New Mexico counties by land area

Together these 10 cover about 47% of New Mexico's land area and hold about 22% of its residents.

The 10 most populous New Mexico counties

These 10 hold about 80% of New Mexico's residents in the 2023 estimates.

The 5 smallest New Mexico counties by land area

Most and least crowded

• Most people per square mile: Bernalillo County, about 578 (then Los Alamos County, 178, and Santa Fe County, 82)
• Fewest people per square mile: Harding County, about 0.3 (then Catron County, 0.6, and De Baca County, 0.7)

Counties with the most water

The Census Bureau reports water separately from land. It counts lakes, reservoirs, rivers and, for coastal and Great Lakes counties, the water inside the county boundary.

• Sierra County: about 57 sq mi of water, 1% of its total area
• Rio Arriba County: about 35 sq mi of water, 1% of its total area
• Eddy County: about 22 sq mi of water, 1% of its total area

Using these numbers in a land search

• Land area is not parcel count. A large rural county can hold fewer parcels than a small suburban one, so size alone says little about how busy its parcel map is.
• Search, don't scroll. In a big county, type an address, owner name or parcel number into the viewer's search box, where it has one, instead of panning across the map.
• Records follow the county line. Deeds, plats and tax bills are kept by the county where the parcel sits, so a tract that crosses a county line usually has a parcel number in each county.
• Rounded figures. Land and water areas are rounded to whole square miles. People per square mile is the 2023 estimate divided by land area.

Related guides

• New Mexico county GIS websites by viewer
• New Mexico landowner maps for hunting
• Colorado–New Mexico border counties
• New Mexico–Texas border counties

More: All New Mexico counties on Platbookmapper

Sources

• U.S. Census Bureau Gazetteer files, 2020 county land and water area.
• U.S. Census Bureau, Population Estimates Program, county totals, Vintage 2023 (July 1, 2023 estimates)
• Platbookmapper county GIS directory (live data file behind our county pages, pulled October 21, 2026) for each county's official parcel viewer.
• County seats: Wikidata (county seat property), cross-checked against Census place names.