County outline
Where Johnson County is located
Area breakdown
Land accounts for 99.5% of Johnson County’s measured area and water for 0.5%. Its combined area converts to 2,158 square kilometers or approximately 533,242 acres.
Green: land · blue: water
| Measurement | Square miles | Square kilometers | Acres |
|---|---|---|---|
| Land | 829.262 | 2,147.779 | 530,727.7 |
| Water | 3.929 | 10.176 | 2,514.6 |
| Total | 833.191 | 2,157.955 | 533,242.2 |
How Johnson County compares
By original Census land area, Johnson County ranks #8 of 115 in Missouri and #1017 of 3,222 nationally. National rankings include the 50 states, District of Columbia, and Puerto Rico.
Its land area is 1.401 times the Missouri county-equivalent median of 592 square miles. It accounts for 1.2% of the combined county land area in the state.
See the complete Missouri ranking · What counts as a county equivalent?
Population and density of Johnson County
The Census Bureau estimates that 56,670 people lived in Johnson County on July 1, 2025. That ranks #950 of 3,222 county equivalents nationally and #21 of 115 in Missouri. Since the April 1, 2020 estimates base of 54,011, the population has grown by 2,659 (+4.9%), compared with +1.9% for Missouri as a whole.
With 829.3 square miles of land, that is 68 people per square mile (26 per km²), placing Johnson County #1,276 nationally for density and #26 in Missouri. The median county equivalent has 47 people per square mile; the Missouri median is 31. Put another way, there are about 9.4 acres of land per resident.
| July 1 | 2020 | 2021 | 2022 | 2023 | 2024 | 2025 |
|---|---|---|---|---|---|---|
| Estimate | 54,023 | 54,209 | 54,406 | 55,051 | 55,824 | 56,670 |
| Change | — | +186 | +197 | +645 | +773 | +846 |
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 Johnson County
7 incorporated places lie at least partly in Johnson County. Together they are home to 26,936 people (47.5%); the other 29,734 (52.5%) live outside any incorporated place, in unincorporated communities and rural areas.
The largest is Warrensburg city, with 20,283 residents in the county. Among places with at least 1,000 residents in 2020, Knob Noster city grew fastest since then (+8.9%).
| Incorporated place | Population 2025 | Since 2020 | Land mi² |
|---|---|---|---|
| Warrensburg cityCounty seat | 20,283 | +5% | 9.409 |
| Knob Noster city | 2,997 | +8.9% | 2.881 |
| Holden city | 2,347 | +6.4% | 2.411 |
| Leeton city | 565 | +6.4% | 0.516 |
| Chilhowee town | 295 | +2.8% | 0.361 |
| Kingsville city | 251 | +4.6% | 0.309 |
| Centerview city | 198 | +4.8% | 0.194 |
Population: U.S. Census Bureau Vintage 2025 subcounty estimates, counting only the part of each place inside Johnson County. Land: 2026 Census Gazetteer, for the whole place even where it extends into other counties. How communities are listed.
Metropolitan area
Johnson County is a central county of the Warrensburg, MO Micropolitan Statistical Area. Johnson County is the area’s only county equivalent, so the micro area has the same 829.3 square miles of land. By combined land it ranks #248 of 542 micropolitan areas, and #187 by population. It belongs to the Kansas City-Overland Park-Kansas City, MO-KS Combined Statistical Area.
ZIP codes
19 ZIP Code Tabulation Areas have land in Johnson County; 8 of them have most of their land inside the county, and the others mainly cover neighboring areas.
64011640196402064037640406406164070640766408064093647266473364747647616530565332653366535165360
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 Johnson County
Johnson County shares a land border with 5 county equivalents. It has more land than every one of them. The largest neighbor is Henry County (696.9 mi²) and the smallest is Jackson County (604.7 mi²). Together with its neighbors, Johnson County forms a block of 4,138.1 mi² of land, of which it holds 20%.
| Bordering county equivalent | Land mi² | Size vs. Johnson | Compare |
|---|---|---|---|
| Henry County | 696.9 | 1.2× smaller | Compare |
| Cass County | 696.6 | 1.2× smaller | Compare |
| Pettis County | 682.2 | 1.2× smaller | Compare |
| Lafayette County | 628.3 | 1.3× smaller | Compare |
| Jackson County | 604.7 | 1.4× smaller | Compare |
How big is Johnson County compared with U.S. states?
Johnson County has less land than any of the 50 states. Rhode Island, the smallest state by land area, has 1,033.9 mi², about 1.2 times as much. Missouri’s county land could hold about 83 areas the size of Johnson County.
Another way to picture it: the same land area would fill a square about 28.8 miles (46.3 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 Johnson County?
Johnson County has more land than 2,205 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 Johnson County at #1,113 nationally by total area, 96 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 0.5%, compared with a national county-equivalent median of 1.2% — 0.7 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 Johnson County in the national ranking. They can be in different states and are not necessarily geographic neighbors.
| Land rank | County equivalent | Land mi² | Comparison |
|---|---|---|---|
| #1016 | Jackson County, Texas | 829.4 | Compare |
| #1017 | Johnson County, Missouri | 829.3 | This county |
| #1018 | Drew County, Arkansas | 828.7 | 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 38.741530, -93.811866. 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: 2,147,779,824 m²; AWATER: 10,176,754 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 Johnson County?
Johnson County, Missouri has 829.3 square miles (2,147.8 km²) of land and 3.929 square miles of water, for a total area of 833.2 square miles. It ranks #1017 of 3,222 U.S. county equivalents by land area.
Is Johnson County the largest county in Missouri?
No. Johnson County ranks #8 of 115 in Missouri by land area. The largest is Texas County, with 1,177.3 square miles of land.
What counties border Johnson County?
Johnson County shares a land border with Lafayette County, Henry County, Pettis County, Cass County, and Jackson County.
What is the population of Johnson County?
The Census Bureau estimates Johnson County had 56,670 residents on July 1, 2025, ranking #950 of 3,222 county equivalents. That is 68 people per square mile of land.
What is the county seat of Johnson County?
The county seat of Johnson County is Warrensburg.
What cities and towns are in Johnson County?
Johnson County has 7 incorporated places. The most populous five are Warrensburg city, Knob Noster city, Holden city, Leeton city, and Chilhowee town; 29,734 residents live outside any incorporated place.
Is Johnson County part of a metropolitan area?
Yes. It is a central county of the Warrensburg, MO Micropolitan Statistical Area.
How many ZIP codes are in Johnson County?
19 ZIP Code Tabulation Areas have land in Johnson 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 Johnson County compare with U.S. states?
It has less land than every state. Rhode Island, the smallest, has 1.2 times as much land.
How many acres of land are in Johnson County?
The land measurement converts to approximately 530,728 acres. Including water, total area is approximately 533,242 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.