County outline
Where Allegan County is located
Area breakdown
Land accounts for 45% of Allegan County’s measured area and water for 55%. Its combined area converts to 4,748.2 square kilometers or approximately 1,173,305 acres.
Green: land · blue: water
| Measurement | Square miles | Square kilometers | Acres |
|---|---|---|---|
| Land | 825.43 | 2,137.854 | 528,275.2 |
| Water | 1,007.859 | 2,610.343 | 645,029.8 |
| Total | 1,833.289 | 4,748.197 | 1,173,305 |
How Allegan County compares
By original Census land area, Allegan County ranks #19 of 83 in Michigan and #1025 of 3,222 nationally. National rankings include the 50 states, District of Columbia, and Puerto Rico.
Its land area is 1.454 times the Michigan county-equivalent median of 567.8 square miles. It accounts for 1.5% of the combined county land area in the state.
See the complete Michigan ranking · What counts as a county equivalent?
Population and density of Allegan County
The Census Bureau estimates that 123,188 people lived in Allegan County on July 1, 2025. That ranks #532 of 3,222 county equivalents nationally and #18 of 83 in Michigan. Since the April 1, 2020 estimates base of 120,511, the population has grown by 2,677 (+2.2%), compared with +0.5% for Michigan as a whole.
With 825.4 square miles of land, that is 149 people per square mile (58 per km²), placing Allegan County #775 nationally for density and #22 in Michigan. The median county equivalent has 47 people per square mile; the Michigan median is 62. Put another way, there are about 4.3 acres of land per resident.
| July 1 | 2020 | 2021 | 2022 | 2023 | 2024 | 2025 |
|---|---|---|---|---|---|---|
| Estimate | 120,666 | 121,082 | 121,299 | 121,935 | 122,567 | 123,188 |
| Change | — | +416 | +217 | +636 | +632 | +621 |
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 Allegan County
Allegan County is divided into 33 municipalities and townships. In Michigan, county subdivisions are local governments, and together they cover all of the county’s land and residents.
The most populous is Holland city, with 8,029 residents (6.5% of the county). The largest by land is Casco township, at 38.9 mi², or 4.7% of the county’s land. The county seat, Allegan city, has 5,127 residents. Among those with at least 1,000 residents in 2020, Saugatuck township grew fastest since then (+6.7%).
| County subdivision | Population 2025 | Since 2020 | Land mi² | Share of county land |
|---|---|---|---|---|
| Holland city | 8,029 | +3.9% | 8.518 | 1% |
| Dorr township | 7,918 | −0.1% | 36.1 | 4.4% |
| Leighton township | 7,374 | +5.2% | 34.9 | 4.2% |
| Laketown township | 6,257 | +5.5% | 21.6 | 2.6% |
| Gun Plain township | 6,169 | +0.3% | 34 | 4.1% |
| Otsego township | 6,001 | +1.6% | 33.3 | 4% |
| Salem township | 5,269 | +2.3% | 35.7 | 4.3% |
| Allegan cityCounty seat | 5,127 | −1.7% | 3.844 | 0.5% |
| Allegan townshipCounty seat | 4,894 | +4.2% | 30.4 | 3.7% |
| Wayland city | 4,531 | +2.3% | 2.962 | 0.4% |
| Otsego city | 4,045 | −1.7% | 2.033 | 0.2% |
| Heath township | 4,017 | +1.8% | 35.4 | 4.3% |
| Lee township | 3,836 | +0.9% | 35.2 | 4.3% |
| Plainwell city | 3,722 | −1.8% | 2.075 | 0.3% |
| Saugatuck township | 3,688 | +6.7% | 23.1 | 2.8% |
Show the other 18 subdivisions
| Name | Population 2025 | Since 2020 | Land mi² |
|---|---|---|---|
| Wayland township | 3,620 | +1.5% | 32.6 |
| Manlius township | 3,433 | +3.4% | 35.2 |
| Overisel township | 3,169 | +0.9% | 35.6 |
| Casco township | 2,937 | +5% | 38.9 |
| Fillmore township | 2,934 | +6.1% | 28 |
| Hopkins township | 2,754 | +0.1% | 35.7 |
| Martin township | 2,721 | −0.2% | 35.6 |
| Ganges township | 2,676 | +4% | 32.2 |
| Trowbridge township | 2,561 | +1.1% | 34.6 |
| Monterey township | 2,529 | +3.7% | 35.7 |
| Valley township | 2,337 | +5.5% | 32.9 |
| Watson township | 2,264 | +4.1% | 35.3 |
| Cheshire township | 2,258 | +2.2% | 34.8 |
| Clyde township | 2,096 | +1.6% | 34.8 |
| Fennville city | 1,724 | −0.7% | 1.119 |
| Douglas city | 1,411 | +3.5% | 1.779 |
| Saugatuck city | 882 | +1.6% | 1.391 |
| South Haven city | 5 | 0% | 0.042 |
Population: U.S. Census Bureau Vintage 2025 subcounty estimates, counting only the part of each subdivision inside Allegan County. Land: 2026 Census Gazetteer. How communities are listed.
Metropolitan area
Allegan County is a central county of the Holland, MI Micropolitan Statistical Area. Allegan County is the area’s only county equivalent, so the micro area has the same 825.4 square miles of land. By combined land it ranks #253 of 542 micropolitan areas, and #17 by population. It belongs to the Grand Rapids-Wyoming, MI Combined Statistical Area.
ZIP codes
25 ZIP Code Tabulation Areas have land in Allegan County; 15 of them have most of their land inside the county, and the others mainly cover neighboring areas.
49010490264905549056490704907849080490904931549316493234932849333493354934449348494064940849419494234942649434494504945349464
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 Allegan County
Allegan County shares a land border with 5 county equivalents. It has more land than 4 of them. The largest neighbor is Kent County (849.5 mi²) and the smallest is Barry County (553.1 mi²). Together with its neighbors, Allegan County forms a block of 3,961.4 mi² of land, of which it holds 20.8%.
| Bordering county equivalent | Land mi² | Size vs. Allegan | Compare |
|---|---|---|---|
| Kent County | 849.5 | about the same | Compare |
| Van Buren County | 607.8 | 1.4× smaller | Compare |
| Ottawa County | 563.5 | 1.5× smaller | Compare |
| Kalamazoo County | 562 | 1.5× smaller | Compare |
| Barry County | 553.1 | 1.5× smaller | Compare |
How big is Allegan County compared with U.S. states?
Allegan County has less land than any of the 50 states. Rhode Island, the smallest state by land area, has 1,033.9 mi², about 1.3 times as much. Michigan’s county land could hold about 69 areas the size of Allegan County.
Another way to picture it: the same land area would fill a square about 28.7 miles (46.2 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 Allegan County?
Allegan County has more land than 2,197 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 Allegan County at #361 nationally by total area, 664 places closer to the top than its land rank. The water assigned to this geography moves it ahead of some county equivalents with more land.
Its water share is 55%, compared with a national county-equivalent median of 1.2% — 53.8 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 Allegan County in the national ranking. They can be in different states and are not necessarily geographic neighbors.
| Land rank | County equivalent | Land mi² | Comparison |
|---|---|---|---|
| #1024 | Vernon County, Missouri | 826.4 | Compare |
| #1025 | Allegan County, Michigan | 825.4 | This county |
| #1026 | Sherman County, Oregon | 823.6 | 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 42.421236, -86.261404. 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: 2,137,854,636 m²; AWATER: 2,610,343,994 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 Allegan County?
Allegan County, Michigan has 825.4 square miles (2,137.9 km²) of land and 1,007.9 square miles of water, for a total area of 1,833.3 square miles. It ranks #1025 of 3,222 U.S. county equivalents by land area.
Is Allegan County the largest county in Michigan?
No. Allegan County ranks #19 of 83 in Michigan by land area. The largest is Marquette County, with 1,809.1 square miles of land.
What counties border Allegan County?
Allegan County shares a land border with Van Buren County, Barry County, Ottawa County, Kent County, and Kalamazoo County.
What is the population of Allegan County?
The Census Bureau estimates Allegan County had 123,188 residents on July 1, 2025, ranking #532 of 3,222 county equivalents. That is 149 people per square mile of land.
What is the county seat of Allegan County?
The county seat of Allegan County is Allegan.
What cities and towns are in Allegan County?
Allegan County has 33 county subdivisions (cities, towns and townships). The most populous five are Holland city, Dorr township, Leighton township, Laketown township, and Gun Plain township.
Is Allegan County part of a metropolitan area?
Yes. It is a central county of the Holland, MI Micropolitan Statistical Area.
How many ZIP codes are in Allegan County?
25 ZIP Code Tabulation Areas have land in Allegan County, and 15 of them have most of their land inside the county. Census ZIP Code Tabulation Areas approximate USPS ZIP Code areas.
How does Allegan County compare with U.S. states?
It has less land than every state. Rhode Island, the smallest, has 1.3 times as much land.
How many acres of land are in Allegan County?
The land measurement converts to approximately 528,275 acres. Including water, total area is approximately 1,173,305 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.