County outline
Where Monroe County is located
Area breakdown
Land accounts for 80.8% of Monroe County’s measured area and water for 19.2%. Its combined area converts to 1,761 square kilometers or approximately 435,158 acres.
Green: land · blue: water
| Measurement | Square miles | Square kilometers | Acres |
|---|---|---|---|
| Land | 549.358 | 1,422.831 | 351,589.1 |
| Water | 130.577 | 338.193 | 83,569.3 |
| Total | 679.935 | 1,761.024 | 435,158.4 |
How Monroe County compares
By original Census land area, Monroe County ranks #60 of 83 in Michigan and #1901 of 3,222 nationally. National rankings include the 50 states, District of Columbia, and Puerto Rico.
Its land area is 0.967 times the Michigan county-equivalent median of 567.8 square miles. It accounts for 1% of the combined county land area in the state.
See the complete Michigan ranking · What counts as a county equivalent?
Population and density of Monroe County
The Census Bureau estimates that 156,004 people lived in Monroe County on July 1, 2025. That ranks #456 of 3,222 county equivalents nationally and #15 of 83 in Michigan. Since the April 1, 2020 estimates base of 154,821, the population has grown by 1,183 (+0.8%), compared with +0.5% for Michigan as a whole.
With 549.4 square miles of land, that is 284 people per square mile (110 per km²), placing Monroe County #530 nationally for density and #12 in Michigan. The median county equivalent has 47 people per square mile; the Michigan median is 62. Put another way, there are about 2.3 acres of land per resident.
| July 1 | 2020 | 2021 | 2022 | 2023 | 2024 | 2025 |
|---|---|---|---|---|---|---|
| Estimate | 154,912 | 155,587 | 155,376 | 155,563 | 155,870 | 156,004 |
| Change | — | +675 | −211 | +187 | +307 | +134 |
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 Monroe County
Monroe County is divided into 20 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 Bedford township, with 32,013 residents (20.5% of the county). The largest by land is Dundee township, at 48.2 mi², or 8.8% of the county’s land. The county seat, Monroe city, has 20,076 residents. Among those with at least 1,000 residents in 2020, Dundee township grew fastest since then (+7.7%).
| County subdivision | Population 2025 | Since 2020 | Land mi² | Share of county land |
|---|---|---|---|---|
| Bedford township | 32,013 | +0.6% | 39.2 | 7.1% |
| Frenchtown township | 21,753 | +0.9% | 41.7 | 7.6% |
| Monroe cityCounty seat | 20,076 | −1.9% | 9.046 | 1.6% |
| Monroe charter townshipCounty seat | 14,277 | −0.8% | 16.9 | 3.1% |
| Berlin charter township | 10,123 | +2.3% | 32 | 5.8% |
| Dundee township | 8,780 | +7.7% | 48.2 | 8.8% |
| Ash township | 8,013 | +1.9% | 34.6 | 6.3% |
| Raisinville township | 6,136 | +3.5% | 48.1 | 8.8% |
| Ida township | 4,808 | +0.3% | 36.8 | 6.7% |
| Whiteford township | 4,618 | +0.4% | 39.7 | 7.2% |
| La Salle township | 4,591 | −1.2% | 26.6 | 4.8% |
| Erie township | 4,348 | +1.2% | 23.9 | 4.3% |
| Exeter township | 3,977 | +1.1% | 36.5 | 6.7% |
| Summerfield township | 3,195 | +0.3% | 41.9 | 7.6% |
| London township | 3,006 | +0.7% | 35.8 | 6.5% |
Show the other 5 subdivisions
| Name | Population 2025 | Since 2020 | Land mi² |
|---|---|---|---|
| Milan city | 2,247 | +1.4% | 2.343 |
| Milan township | 1,540 | −1.4% | 34 |
| Luna Pier city | 1,351 | −1.9% | 1.492 |
| Petersburg city | 1,152 | −1.3% | 0.558 |
| Flat Rock city | 0 | — | 0.002 |
Population: U.S. Census Bureau Vintage 2025 subcounty estimates, counting only the part of each subdivision inside Monroe County. Land: 2026 Census Gazetteer. How communities are listed.
Metropolitan area
Monroe County is a central county of the Monroe, MI Metropolitan Statistical Area. Monroe County is the area’s only county equivalent, so the metro area has the same 549.4 square miles of land. By combined land it ranks #350 of 393 metropolitan areas, and #289 by population. It belongs to the Detroit-Warren-Ann Arbor, MI Combined Statistical Area.
ZIP codes
25 ZIP Code Tabulation Areas have land in Monroe County; 17 of them have most of their land inside the county, and the others mainly cover neighboring areas.
48111481174813148133481344814048144481454815748159481604816148162481644816648177481794818248191492284922949238492674927049276
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 Monroe County
Monroe County shares a land border with 4 county equivalents, including 1 in Ohio. It has more land than 1 of them. The largest neighbor is Lenawee County (749.7 mi²) and the smallest is Lucas County (339.7 mi²). Together with its neighbors, Monroe County forms a block of 2,956.5 mi² of land, of which it holds 18.6%.
| Bordering county equivalent | Land mi² | Size vs. Monroe | Compare |
|---|---|---|---|
| Lenawee County | 749.7 | 1.4× larger | Compare |
| Washtenaw County | 706 | 1.3× larger | Compare |
| Wayne County | 611.8 | 1.1× larger | Compare |
| Lucas CountyOhio | 339.7 | 1.6× smaller | Compare |
How big is Monroe County compared with U.S. states?
Monroe County has less land than any of the 50 states. Rhode Island, the smallest state by land area, has 1,033.9 mi², about 1.9 times as much. Michigan’s county land could hold about 103 areas the size of Monroe County.
Another way to picture it: the same land area would fill a square about 23.4 miles (37.7 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 Monroe County?
Monroe County has more land than 1,321 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 Monroe County at #1,494 nationally by total area, 407 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 19.2%, compared with a national county-equivalent median of 1.2% — 18 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 Monroe County in the national ranking. They can be in different states and are not necessarily geographic neighbors.
| Land rank | County equivalent | Land mi² | Comparison |
|---|---|---|---|
| #1900 | Iosco County, Michigan | 549.5 | Compare |
| #1901 | Monroe County, Michigan | 549.4 | This county |
| #1902 | Lancaster County, South Carolina | 549.2 | 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 41.916097, -83.487106. 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: 1,422,829,738 m²; AWATER: 338,191,959 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 Monroe County?
Monroe County, Michigan has 549.4 square miles (1,422.8 km²) of land and 130.6 square miles of water, for a total area of 679.9 square miles. It ranks #1901 of 3,222 U.S. county equivalents by land area.
Is Monroe County the largest county in Michigan?
No. Monroe County ranks #60 of 83 in Michigan by land area. The largest is Marquette County, with 1,809.1 square miles of land.
What counties border Monroe County?
Monroe County shares a land border with Lenawee County, Wayne County, Lucas County, Ohio, and Washtenaw County.
What is the population of Monroe County?
The Census Bureau estimates Monroe County had 156,004 residents on July 1, 2025, ranking #456 of 3,222 county equivalents. That is 284 people per square mile of land.
What is the county seat of Monroe County?
The county seat of Monroe County is Monroe.
What cities and towns are in Monroe County?
Monroe County has 20 county subdivisions (cities, towns and townships). The most populous five are Bedford township, Frenchtown township, Monroe city, Monroe charter township, and Berlin charter township.
Is Monroe County part of a metropolitan area?
Yes. It is a central county of the Monroe, MI Metropolitan Statistical Area.
How many ZIP codes are in Monroe County?
25 ZIP Code Tabulation Areas have land in Monroe County, and 17 of them have most of their land inside the county. Census ZIP Code Tabulation Areas approximate USPS ZIP Code areas.
How does Monroe County compare with U.S. states?
It has less land than every state. Rhode Island, the smallest, has 1.9 times as much land.
How many acres of land are in Monroe County?
The land measurement converts to approximately 351,589 acres. Including water, total area is approximately 435,158 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.