County outline
Where Day County is located
Area breakdown
Land accounts for 94.3% of Day County’s measured area and water for 5.7%. Its combined area converts to 2,825.9 square kilometers or approximately 698,300 acres.
Green: land · blue: water
| Measurement | Square miles | Square kilometers | Acres |
|---|---|---|---|
| Land | 1,028.49 | 2,663.777 | 658,233.6 |
| Water | 62.603 | 162.141 | 40,065.9 |
| Total | 1,091.093 | 2,825.918 | 698,299.5 |
How Day County compares
By original Census land area, Day County ranks #28 of 66 in South Dakota and #644 of 3,222 nationally. National rankings include the 50 states, District of Columbia, and Puerto Rico.
Its land area is 1.131 times the South Dakota county-equivalent median of 909.3 square miles. It accounts for 1.4% of the combined county land area in the state.
See the complete South Dakota ranking · What counts as a county equivalent?
Population and density of Day County
The Census Bureau estimates that 5,484 people lived in Day County on July 1, 2025. That ranks #2,855 of 3,222 county equivalents nationally and #32 of 66 in South Dakota. Since the April 1, 2020 estimates base of 5,452, the population has grown by 32 (+0.6%), compared with +5.5% for South Dakota as a whole.
With 1,028.5 square miles of land, that is 5.3 people per square mile (2.1 per km²), placing Day County #2,834 nationally for density and #34 in South Dakota. The median county equivalent has 47 people per square mile; the South Dakota median is 5.7. Put another way, there are about 120 acres of land per resident.
| July 1 | 2020 | 2021 | 2022 | 2023 | 2024 | 2025 |
|---|---|---|---|---|---|---|
| Estimate | 5,442 | 5,422 | 5,480 | 5,429 | 5,447 | 5,484 |
| Change | — | −20 | +58 | −51 | +18 | +37 |
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 Day County
8 incorporated places lie at least partly in Day County. Together they are home to 2,863 people (52.2%); the other 2,621 (47.8%) live outside any incorporated place, in unincorporated communities and rural areas.
The largest is Webster city, with 1,681 residents in the county.
| Incorporated place | Population 2025 | Since 2020 | Land mi² |
|---|---|---|---|
| Webster cityCounty seat | 1,681 | −2.7% | 1.769 |
| Waubay city | 474 | 0% | 1.456 |
| Bristol city | 278 | −2.8% | 0.522 |
| Roslyn town | 182 | −1.6% | 0.218 |
| Pierpont town | 125 | −4.6% | 0.152 |
| Andover town | 71 | +4.4% | 0.27 |
| Grenville town | 48 | +2.1% | 0.237 |
| Butler town | 4 | 0% | 0.291 |
Population: U.S. Census Bureau Vintage 2025 subcounty estimates, counting only the part of each place inside Day County. Land: 2026 Census Gazetteer, for the whole place even where it extends into other counties. How communities are listed.
Metropolitan area
Day 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
11 ZIP Code Tabulation Areas have land in Day County; 7 of them have most of their land inside the county, and the others mainly cover neighboring areas.
5721957235572395725657261572735727457422574345745457468
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 Day County
Day County shares a land border with 7 county equivalents. It has more land than 4 of them. The largest neighbor is Brown County (1,713 mi²) and the smallest is Grant County (681.4 mi²). Together with its neighbors, Day County forms a block of 8,510.7 mi² of land, of which it holds 12.1%.
| Bordering county equivalent | Land mi² | Size vs. Day | Compare |
|---|---|---|---|
| Brown County | 1,713 | 1.7× larger | Compare |
| Spink County | 1,503.5 | 1.5× larger | Compare |
| Roberts County | 1,101.1 | 1.1× larger | Compare |
| Clark County | 957.5 | 1.1× smaller | Compare |
| Marshall County | 838.1 | 1.2× smaller | Compare |
| Codington County | 687.6 | 1.5× smaller | Compare |
| Grant County | 681.4 | 1.5× smaller | Compare |
How big is Day County compared with U.S. states?
Day County has less land than any of the 50 states. Rhode Island, the smallest state by land area, has 1,033.9 mi², about 1 times as much. South Dakota’s county land could hold about 74 areas the size of Day County.
Another way to picture it: the same land area would fill a square about 32.1 miles (51.6 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 Day County?
Day County has more land than 2,578 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 Day County at #673 nationally by total area, 29 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 5.7%, compared with a national county-equivalent median of 1.2% — 4.6 percentage points higher. 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 Day County in the national ranking. They can be in different states and are not necessarily geographic neighbors.
| Land rank | County equivalent | Land mi² | Comparison |
|---|---|---|---|
| #643 | Rich County, Utah | 1,028.8 | Compare |
| #644 | Day County, South Dakota | 1,028.5 | This county |
| #645 | Westmoreland County, Pennsylvania | 1,027.7 | 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 45.355161, -97.581430. 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: 2,663,775,884 m²; AWATER: 162,141,027 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 Day County?
Day County, South Dakota has 1,028.5 square miles (2,663.8 km²) of land and 62.6 square miles of water, for a total area of 1,091.1 square miles. It ranks #644 of 3,222 U.S. county equivalents by land area.
Is Day County the largest county in South Dakota?
No. Day County ranks #28 of 66 in South Dakota by land area. The largest is Meade County, with 3,470.9 square miles of land.
What counties border Day County?
Day County shares a land border with Marshall County, Brown County, Clark County, Roberts County, Codington County, Grant County, and Spink County.
What is the population of Day County?
The Census Bureau estimates Day County had 5,484 residents on July 1, 2025, ranking #2,855 of 3,222 county equivalents. That is 5.3 people per square mile of land.
What is the county seat of Day County?
The county seat of Day County is Webster.
What cities and towns are in Day County?
Day County has 8 incorporated places. The most populous five are Webster city, Waubay city, Bristol city, Roslyn town, and Pierpont town; 2,621 residents live outside any incorporated place.
Is Day County part of a metropolitan area?
No. Day County is outside every metropolitan and micropolitan statistical area in the July 2023 OMB delineation.
How many ZIP codes are in Day County?
11 ZIP Code Tabulation Areas have land in Day County, and 7 of them have most of their land inside the county. Census ZIP Code Tabulation Areas approximate USPS ZIP Code areas.
How does Day County compare with U.S. states?
It has less land than every state. Rhode Island, the smallest, has 1 times as much land.
How many acres of land are in Day County?
The land measurement converts to approximately 658,234 acres. Including water, total area is approximately 698,300 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.