County outline
Where San Juan County is located
Area breakdown
Land accounts for 99.6% of San Juan County’s measured area and water for 0.4%. Its combined area converts to 14,344.5 square kilometers or approximately 3,544,593 acres.
Green: land · blue: water
| Measurement | Square miles | Square kilometers | Acres |
|---|---|---|---|
| Land | 5,517.23 | 14,289.56 | 3,531,027.2 |
| Water | 21.197 | 54.9 | 13,566.1 |
| Total | 5,538.427 | 14,344.46 | 3,544,593.3 |
How San Juan County compares
By original Census land area, San Juan County ranks #6 of 33 in New Mexico and #67 of 3,222 nationally. National rankings include the 50 states, District of Columbia, and Puerto Rico.
Its land area is 1.468 times the New Mexico county-equivalent median of 3,758 square miles. It accounts for 4.5% of the combined county land area in the state.
See the complete New Mexico ranking · What counts as a county equivalent?
Population and density of San Juan County
The Census Bureau estimates that 120,340 people lived in San Juan County on July 1, 2025. That ranks #544 of 3,222 county equivalents nationally and #5 of 33 in New Mexico. Since the April 1, 2020 estimates base of 121,665, the population has declined by 1,325 (−1.1%), compared with +0.4% for New Mexico as a whole.
With 5,517.2 square miles of land, that is 22 people per square mile (8.4 per km²), placing San Juan County #2,262 nationally for density and #8 in New Mexico. The median county equivalent has 47 people per square mile; the New Mexico median is 6.9. Put another way, there are about 29 acres of land per resident.
| July 1 | 2020 | 2021 | 2022 | 2023 | 2024 | 2025 |
|---|---|---|---|---|---|---|
| Estimate | 121,384 | 121,005 | 120,504 | 120,754 | 120,525 | 120,340 |
| Change | — | −379 | −501 | +250 | −229 | −185 |
U.S. Census Bureau, Vintage 2025 population estimates. Estimates are revised each year and are not decennial census counts. Density divides the whole population by the whole county’s land area, so it describes an average, not how settlement is distributed within the county. Population sources and methods.
Cities and towns in San Juan County
4 incorporated places lie at least partly in San Juan County. Together they are home to 60,053 people (49.9%); the other 60,287 (50.1%) live outside any incorporated place, in unincorporated communities and rural areas.
The largest is Farmington city, with 46,055 residents in the county. The county seat, Aztec city, has 6,091 residents.
| Incorporated place | Population 2025 | Since 2020 | Land mi² |
|---|---|---|---|
| Farmington city | 46,055 | −1.2% | 34.5 |
| Bloomfield city | 7,335 | −1.3% | 18.6 |
| Aztec cityCounty seat | 6,091 | −1.9% | 17.1 |
| Kirtland town | 572 | −2.1% | 1.722 |
Population: U.S. Census Bureau Vintage 2025 subcounty estimates, counting only the part of each place inside San Juan County. Land: 2026 Census Gazetteer, for the whole place even where it extends into other counties. How communities are listed.
Metropolitan area
San Juan County is a central county of the Farmington, NM Metropolitan Statistical Area. San Juan County is the area’s only county equivalent, so the metro area has the same 5,517.2 square miles of land. By combined land it ranks #41 of 393 metropolitan areas, and #337 by population.
ZIP codes
22 ZIP Code Tabulation Areas have land in San Juan County; 16 of them have most of their land inside the county, and the others mainly cover neighboring areas.
81137865148703787313873258732887364874018740287410874128741387415874168741787418874198742087421874558746187499
ZIP Code Tabulation Areas are the Census Bureau’s approximations of USPS ZIP Code service areas, from the 2020 Census relationship files. Lighter codes have less than half of their land in this county. Post-office-box and single-address ZIP Codes have no tabulation area.
Counties bordering San Juan County
San Juan County shares a land border with 7 county equivalents, including 4 in Arizona and Colorado. It has more land than 5 of them. The largest neighbor is Apache County (11,198.4 mi²) and the smallest is Archuleta County (1,350.1 mi²). Together with its neighbors, San Juan County forms a block of 36,806.9 mi² of land, of which it holds 15%.
| Bordering county equivalent | Land mi² | Size vs. San Juan | Compare |
|---|---|---|---|
| Apache CountyArizona | 11,198.4 | 2× larger | Compare |
| Rio Arriba County | 5,860.9 | 1.1× larger | Compare |
| McKinley County | 5,451.1 | about the same | Compare |
| Sandoval County | 3,710.2 | 1.5× smaller | Compare |
| Montezuma CountyColorado | 2,029.3 | 2.7× smaller | Compare |
| La Plata CountyColorado | 1,689.7 | 3.3× smaller | Compare |
| Archuleta CountyColorado | 1,350.1 | 4.1× smaller | Compare |
How big is San Juan County compared with U.S. states?
San Juan County has more land than 3 of the 50 states. It is about 1.1 times the land area of Connecticut (4,842.5 mi²), while Hawaii, the next larger state, has 1.2 times as much land (6,422.6 mi²). New Mexico’s county land could hold about 22 areas the size of San Juan County.
Another way to picture it: the same land area would fill a square about 74.3 miles (119.5 km) on each side. Real county shapes are rarely square, so this is a scale reference rather than a width or driving distance.
State figures are the sums of each state’s county-equivalent land measurements in the same Census release, so states and counties are compared on the same basis. Published state totals can differ slightly because of rounding. Compare all states · Counties bigger than entire states.
What stands out about San Juan County?
San Juan County has more land than 3,155 of the other 3,221 county equivalents in the dataset.
A median is the middle county-equivalent measurement, not the average of the largest and smallest. All three bars use the same linear scale. Very small areas may appear as a thin sliver; the labels retain their values.
Does including water change its rank?
Using land plus water places San Juan County at #70 nationally by total area, 3 places farther from the top than its land rank. Other county equivalents gain more area when their water measurements are included.
Its water share is 0.4%, compared with a national county-equivalent median of 1.2% — 0.8 percentage points lower. This describes the statistical geography’s land/water mix, not flood exposure or developable land.
Closest positions in the national land ranking
These entries sit immediately beside San Juan County in the national ranking. They can be in different states and are not necessarily geographic neighbors.
| Land rank | County equivalent | Land mi² | Comparison |
|---|---|---|---|
| #66 | Lander County, Nevada | 5,519.2 | Compare |
| #67 | San Juan County, New Mexico | 5,517.2 | This county |
| #68 | Yuma County, Arizona | 5,513.8 | Compare |
Calculated from the same Census release as the area table. Total-area order uses original ALAND + AWATER; water shares and chart labels use published square miles. Calculation details.
Representative coordinates
The Census internal point is 36.540774, -108.343307. It represents a location inside the geography; it is not necessarily the centroid or the address of a courthouse.
Source and precision
U.S. Census Bureau, 2026 Gazetteer Files, Counties. Original ALAND: 14,289,558,351 m²; AWATER: 54,900,281 m². Rankings use ALAND; exact ties use ascending GEOID. Tables preserve Census-published square miles to three decimals, with conversions based on those values.
Common questions
How big is San Juan County?
San Juan County, New Mexico has 5,517.2 square miles (14,289.6 km²) of land and 21.2 square miles of water, for a total area of 5,538.4 square miles. It ranks #67 of 3,222 U.S. county equivalents by land area.
Is San Juan County the largest county in New Mexico?
No. San Juan County ranks #6 of 33 in New Mexico by land area. The largest is Catron County, with 6,924.2 square miles of land.
What counties border San Juan County?
San Juan County shares a land border with McKinley County, Apache County, Arizona, Rio Arriba County, La Plata County, Colorado, Montezuma County, Colorado, Sandoval County, and Archuleta County, Colorado.
What is the population of San Juan County?
The Census Bureau estimates San Juan County had 120,340 residents on July 1, 2025, ranking #544 of 3,222 county equivalents. That is 22 people per square mile of land.
What is the county seat of San Juan County?
The county seat of San Juan County is Aztec.
What cities and towns are in San Juan County?
San Juan County has 4 incorporated places. The most populous are Farmington city, Bloomfield city, Aztec city, and Kirtland town; 60,287 residents live outside any incorporated place.
Is San Juan County part of a metropolitan area?
Yes. It is a central county of the Farmington, NM Metropolitan Statistical Area.
How many ZIP codes are in San Juan County?
22 ZIP Code Tabulation Areas have land in San Juan County, and 16 of them have most of their land inside the county. Census ZIP Code Tabulation Areas approximate USPS ZIP Code areas.
How does San Juan County compare with U.S. states?
It has more land than 3 of the 50 states, including Connecticut (4,842.5 square miles of land).
How many acres of land are in San Juan County?
The land measurement converts to approximately 3,531,027 acres. Including water, total area is approximately 3,544,593 acres. One square mile equals 640 acres.
Why might another source show a different area?
Check whether it reports land or total area, its Census vintage, and its rounding. Our guide explains how to reconcile county area figures.
Can this establish a property boundary?
No. Statistical measurements and generalized maps do not establish property lines. Consult the relevant local surveying or land-records authority.