County outline
Where Knox County is located
Area breakdown
Land accounts for 99.2% of Knox County’s measured area and water for 0.8%. Its combined area converts to 1,371.8 square kilometers or approximately 338,969 acres.
Green: land · blue: water
| Measurement | Square miles | Square kilometers | Acres |
|---|---|---|---|
| Land | 525.498 | 1,361.034 | 336,318.7 |
| Water | 4.141 | 10.725 | 2,650.2 |
| Total | 529.639 | 1,371.759 | 338,969 |
How Knox County compares
By original Census land area, Knox County ranks #21 of 88 in Ohio and #1991 of 3,222 nationally. National rankings include the 50 states, District of Columbia, and Puerto Rico.
Its land area is 1.205 times the Ohio county-equivalent median of 436 square miles. It accounts for 1.3% of the combined county land area in the state.
See the complete Ohio ranking · What counts as a county equivalent?
Population and density of Knox County
The Census Bureau estimates that 64,002 people lived in Knox County on July 1, 2025. That ranks #864 of 3,222 county equivalents nationally and #39 of 88 in Ohio. Since the April 1, 2020 estimates base of 62,719, the population has grown by 1,283 (+2%), compared with +0.9% for Ohio as a whole.
With 525.5 square miles of land, that is 122 people per square mile (47 per km²), placing Knox County #868 nationally for density and #43 in Ohio. The median county equivalent has 47 people per square mile; the Ohio median is 120. Put another way, there are about 5.3 acres of land per resident.
| July 1 | 2020 | 2021 | 2022 | 2023 | 2024 | 2025 |
|---|---|---|---|---|---|---|
| Estimate | 62,804 | 62,505 | 63,103 | 63,186 | 63,564 | 64,002 |
| Change | — | −299 | +598 | +83 | +378 | +438 |
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 Knox County
8 incorporated places lie at least partly in Knox County. Together they are home to 25,245 people (39.4%); the other 38,757 (60.6%) live outside any incorporated place, in unincorporated communities and rural areas.
The largest is Mount Vernon city, with 17,287 residents in the county. Among places with at least 1,000 residents in 2020, Mount Vernon city grew fastest since then (+1.3%).
| Incorporated place | Population 2025 | Since 2020 | Land mi² |
|---|---|---|---|
| Mount Vernon cityCounty seat | 17,287 | +1.3% | 9.875 |
| Fredericktown village | 2,658 | +0.4% | 1.984 |
| Gambier village | 2,233 | +0.6% | 0.937 |
| Centerburg village | 1,691 | −1.9% | 0.967 |
| Danville village | 1,025 | +0.1% | 0.591 |
| Martinsburg village | 222 | −1.8% | 0.177 |
| Brinkhaven village | 110 | −2.7% | 0.185 |
| Utica villageAlso in 1 other county | 19 | 0% | 1.745 |
Population: U.S. Census Bureau Vintage 2025 subcounty estimates, counting only the part of each place inside Knox County. Land: 2026 Census Gazetteer, for the whole place even where it extends into other counties. How communities are listed.
Metropolitan area
Knox County is a central county of the Mount Vernon, OH Micropolitan Statistical Area. Knox County is the area’s only county equivalent, so the micro area has the same 525.5 square miles of land. By combined land it ranks #418 of 542 micropolitan areas, and #144 by population. It belongs to the Columbus-Marion-Zanesville, OH Combined Statistical Area.
ZIP codes
16 ZIP Code Tabulation Areas have land in Knox County; 8 of them have most of their land inside the county, and the others mainly cover neighboring areas.
43005430064301143014430194302243028430374305043080438224384344628448134482244842
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 Knox County
Knox County shares a land border with 7 county equivalents. It has more land than 5 of them. The largest neighbor is Licking County (682.4 mi²) and the smallest is Morrow County (406.1 mi²). Together with its neighbors, Knox County forms a block of 3,961.9 mi² of land, of which it holds 13.3%.
| Bordering county equivalent | Land mi² | Size vs. Knox | Compare |
|---|---|---|---|
| Licking County | 682.4 | 1.3× larger | Compare |
| Coshocton County | 563.9 | 1.1× larger | Compare |
| Richland County | 495.2 | 1.1× smaller | Compare |
| Delaware County | 443.1 | 1.2× smaller | Compare |
| Ashland County | 423 | 1.2× smaller | Compare |
| Holmes County | 422.6 | 1.2× smaller | Compare |
| Morrow County | 406.1 | 1.3× smaller | Compare |
How big is Knox County compared with U.S. states?
Knox County has less land than any of the 50 states. Rhode Island, the smallest state by land area, has 1,033.9 mi², about 2 times as much. Ohio’s county land could hold about 78 areas the size of Knox County.
Another way to picture it: the same land area would fill a square about 22.9 miles (36.9 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 Knox County?
Knox County has more land than 1,231 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 Knox County at #2,074 nationally by total area, 83 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 0.8%, compared with a national county-equivalent median of 1.2% — 0.4 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 Knox County in the national ranking. They can be in different states and are not necessarily geographic neighbors.
| Land rank | County equivalent | Land mi² | Comparison |
|---|---|---|---|
| #1990 | Jerauld County, South Dakota | 526.1 | Compare |
| #1991 | Knox County, Ohio | 525.5 | This county |
| #1992 | Wayne County, Iowa | 525.5 | 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 40.403602, -82.422379. 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: 1,361,033,262 m²; AWATER: 10,724,359 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 Knox County?
Knox County, Ohio has 525.5 square miles (1,361 km²) of land and 4.141 square miles of water, for a total area of 529.6 square miles. It ranks #1991 of 3,222 U.S. county equivalents by land area.
Is Knox County the largest county in Ohio?
No. Knox County ranks #21 of 88 in Ohio by land area. The largest is Ashtabula County, with 702.4 square miles of land.
What counties border Knox County?
Knox County shares a land border with Licking County, Morrow County, Coshocton County, Richland County, Holmes County, Ashland County, and Delaware County.
What is the population of Knox County?
The Census Bureau estimates Knox County had 64,002 residents on July 1, 2025, ranking #864 of 3,222 county equivalents. That is 122 people per square mile of land.
What is the county seat of Knox County?
The county seat of Knox County is Mount Vernon.
What cities and towns are in Knox County?
Knox County has 8 incorporated places. The most populous five are Mount Vernon city, Fredericktown village, Gambier village, Centerburg village, and Danville village; 38,757 residents live outside any incorporated place.
Is Knox County part of a metropolitan area?
Yes. It is a central county of the Mount Vernon, OH Micropolitan Statistical Area.
How many ZIP codes are in Knox County?
16 ZIP Code Tabulation Areas have land in Knox County, and 8 of them have most of their land inside the county. Census ZIP Code Tabulation Areas approximate USPS ZIP Code areas.
How does Knox County compare with U.S. states?
It has less land than every state. Rhode Island, the smallest, has 2 times as much land.
How many acres of land are in Knox County?
The land measurement converts to approximately 336,319 acres. Including water, total area is approximately 338,969 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.