County outline
Where Dallam County is located
Area breakdown
Land accounts for 99.9% of Dallam County’s measured area and water for 0.1%. Its combined area converts to 3,898.3 square kilometers or approximately 963,285 acres.
Green: land · blue: water
| Measurement | Square miles | Square kilometers | Acres |
|---|---|---|---|
| Land | 1,503.353 | 3,893.666 | 962,145.9 |
| Water | 1.78 | 4.61 | 1,139.2 |
| Total | 1,505.133 | 3,898.277 | 963,285.1 |
How Dallam County compares
By original Census land area, Dallam County ranks #18 of 254 in Texas and #397 of 3,222 nationally. National rankings include the 50 states, District of Columbia, and Puerto Rico.
Its land area is 1.654 times the Texas county-equivalent median of 908.7 square miles. It accounts for 0.6% of the combined county land area in the state.
See the complete Texas ranking · What counts as a county equivalent?
Population and density of Dallam County
The Census Bureau estimates that 7,508 people lived in Dallam County on July 1, 2025. That ranks #2,692 of 3,222 county equivalents nationally and #180 of 254 in Texas. Since the April 1, 2020 estimates base of 7,135, the population has grown by 373 (+5.2%), compared with +8.8% for Texas as a whole.
With 1,503.4 square miles of land, that is 5 people per square mile (1.9 per km²), placing Dallam County #2,854 nationally for density and #198 in Texas. The median county equivalent has 47 people per square mile; the Texas median is 22. Put another way, there are about 128 acres of land per resident.
| July 1 | 2020 | 2021 | 2022 | 2023 | 2024 | 2025 |
|---|---|---|---|---|---|---|
| Estimate | 7,137 | 7,181 | 7,247 | 7,302 | 7,447 | 7,508 |
| Change | — | +44 | +66 | +55 | +145 | +61 |
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 Dallam County
2 incorporated places lie at least partly in Dallam County. Together they are home to 6,262 people (83.4%); the other 1,246 (16.6%) live outside any incorporated place, in unincorporated communities and rural areas.
The largest is Dalhart city, with 5,770 residents in the county (the city extends into 1 other county).
| Incorporated place | Population 2025 | Since 2020 | Land mi² |
|---|---|---|---|
| Dalhart cityCounty seat · Also in 1 other county | 5,770 | +5% | 4.783 |
| Texline town | 492 | +8.4% | 1.016 |
Population: U.S. Census Bureau Vintage 2025 subcounty estimates, counting only the part of each place inside Dallam County. Land: 2026 Census Gazetteer, for the whole place even where it extends into other counties. How communities are listed.
Metropolitan area
Dallam County is not part of any metropolitan or micropolitan statistical area in the Office of Management and Budget’s July 2023 delineation; 1,306 other county equivalents are also outside one. These areas are built around an urban core of at least 10,000 people plus the counties tied to it by commuting, so counties outside them are generally rural.
ZIP codes
4 ZIP Code Tabulation Areas have land in Dallam County; 3 of them have most of their land inside the county, and the others mainly cover neighboring areas.
79022790517908479087
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 Dallam County
Dallam County shares a land border with 4 county equivalents, including 2 in Oklahoma and New Mexico. It has more land than 2 of them. The largest neighbor is Union County (3,825.1 mi²) and the smallest is Sherman County (922.9 mi²). Together with its neighbors, Dallam County forms a block of 9,548 mi² of land, of which it holds 15.7%.
| Bordering county equivalent | Land mi² | Size vs. Dallam | Compare |
|---|---|---|---|
| Union CountyNew Mexico | 3,825.1 | 2.5× larger | Compare |
| Cimarron CountyOklahoma | 1,834.8 | 1.2× larger | Compare |
| Hartley County | 1,462 | about the same | Compare |
| Sherman County | 922.9 | 1.6× smaller | Compare |
How big is Dallam County compared with U.S. states?
Dallam County has more land than 1 of the 50 states. It is about 1.5 times the land area of Rhode Island (1,033.9 mi²), while Delaware, the next larger state, has 1.3 times as much land (1,948.6 mi²). Texas’s county land could hold about 174 areas the size of Dallam County.
Another way to picture it: the same land area would fill a square about 38.8 miles (62.4 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 Dallam County?
Dallam County has more land than 2,825 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 Dallam County at #447 nationally by total area, 50 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 0.1%, compared with a national county-equivalent median of 1.2% — 1.1 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 Dallam County in the national ranking. They can be in different states and are not necessarily geographic neighbors.
| Land rank | County equivalent | Land mi² | Comparison |
|---|---|---|---|
| #396 | Spink County, South Dakota | 1,503.5 | Compare |
| #397 | Dallam County, Texas | 1,503.4 | This county |
| #398 | Gaines County, Texas | 1,502.4 | 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 36.286370, -102.594020. 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: 3,893,666,624 m²; AWATER: 4,609,040 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 Dallam County?
Dallam County, Texas has 1,503.4 square miles (3,893.7 km²) of land and 1.78 square miles of water, for a total area of 1,505.1 square miles. It ranks #397 of 3,222 U.S. county equivalents by land area.
Is Dallam County the largest county in Texas?
No. Dallam County ranks #18 of 254 in Texas by land area. The largest is Brewster County, with 6,183.8 square miles of land.
What counties border Dallam County?
Dallam County shares a land border with Hartley County, Cimarron County, Oklahoma, Union County, New Mexico, and Sherman County.
What is the population of Dallam County?
The Census Bureau estimates Dallam County had 7,508 residents on July 1, 2025, ranking #2,692 of 3,222 county equivalents. That is 5 people per square mile of land.
What is the county seat of Dallam County?
The county seat of Dallam County is Dalhart.
What cities and towns are in Dallam County?
Dallam County has 2 incorporated places. The most populous are Dalhart city and Texline town; 1,246 residents live outside any incorporated place.
Is Dallam County part of a metropolitan area?
No. Dallam County is outside every metropolitan and micropolitan statistical area in the July 2023 OMB delineation.
How many ZIP codes are in Dallam County?
4 ZIP Code Tabulation Areas have land in Dallam County, and 3 of them have most of their land inside the county. Census ZIP Code Tabulation Areas approximate USPS ZIP Code areas.
How does Dallam County compare with U.S. states?
It has more land than 1 of the 50 states, including Rhode Island (1,033.9 square miles of land).
How many acres of land are in Dallam County?
The land measurement converts to approximately 962,146 acres. Including water, total area is approximately 963,285 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.