County outline
Where Iosco County is located
Area breakdown
Land accounts for 29.1% of Iosco County’s measured area and water for 70.9%. Its combined area converts to 4,895.2 square kilometers or approximately 1,209,641 acres.
Green: land · blue: water
| Measurement | Square miles | Square kilometers | Acres |
|---|---|---|---|
| Land | 549.477 | 1,423.139 | 351,665.3 |
| Water | 1,340.587 | 3,472.104 | 857,975.7 |
| Total | 1,890.064 | 4,895.243 | 1,209,641 |
How Iosco County compares
By original Census land area, Iosco County ranks #59 of 83 in Michigan and #1900 of 3,222 nationally. National rankings include the 50 states, District of Columbia, and Puerto Rico.
Its land area is 0.968 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 Iosco County
The Census Bureau estimates that 25,266 people lived in Iosco County on July 1, 2025. That ranks #1,663 of 3,222 county equivalents nationally and #58 of 83 in Michigan. Since the April 1, 2020 estimates base of 25,232, the population has grown by 34 (+0.1%), compared with +0.5% for Michigan as a whole.
With 549.5 square miles of land, that is 46 people per square mile (18 per km²), placing Iosco County #1,634 nationally for density and #54 in Michigan. The median county equivalent has 47 people per square mile; the Michigan median is 62. Put another way, there are about 14 acres of land per resident.
| July 1 | 2020 | 2021 | 2022 | 2023 | 2024 | 2025 |
|---|---|---|---|---|---|---|
| Estimate | 25,189 | 25,360 | 25,451 | 25,404 | 25,425 | 25,266 |
| Change | — | +171 | +91 | −47 | +21 | −159 |
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 Iosco County
Iosco County is divided into 14 municipalities and townships. In Michigan, county subdivisions are local governments, and together they cover all of the county’s land and residents; a few are unorganized areas without their own government.
The most populous is Oscoda charter township, with 7,158 residents (28.3% of the county), and it is also the largest by land at 122 mi². The county seat, Tawas City city, has 1,830 residents. Among those with at least 1,000 residents in 2020, Tawas township grew fastest since then (+0.3%).
| County subdivision | Population 2025 | Since 2020 | Land mi² | Share of county land |
|---|---|---|---|---|
| Oscoda charter township | 7,158 | +0.3% | 122 | 22.2% |
| Plainfield township | 3,353 | −0.1% | 103.7 | 18.9% |
| East Tawas city | 2,662 | −0.1% | 2.813 | 0.5% |
| Au Sable charter township | 2,025 | +0.1% | 21 | 3.8% |
| Tawas City cityCounty seat | 1,830 | −0.1% | 1.699 | 0.3% |
| Tawas township | 1,737 | +0.3% | 33.4 | 6.1% |
| Baldwin township | 1,607 | −0.2% | 28.4 | 5.2% |
| Grant township | 1,536 | +0.1% | 34.9 | 6.3% |
| Burleigh township | 729 | +0.7% | 34.6 | 6.3% |
| Wilber township | 720 | +0.4% | 72.4 | 13.2% |
| Reno township | 631 | +0.6% | 35.3 | 6.4% |
| Sherman township | 433 | +0.2% | 35.9 | 6.5% |
| Alabaster township | 426 | 0% | 22.2 | 4% |
| Whittemore city | 419 | +0.5% | 1.024 | 0.2% |
Population: U.S. Census Bureau Vintage 2025 subcounty estimates, counting only the part of each subdivision inside Iosco County. Land: 2026 Census Gazetteer. How communities are listed.
Metropolitan area
Iosco 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
12 ZIP Code Tabulation Areas have land in Iosco County; 7 of them have most of their land inside the county, and the others mainly cover neighboring areas.
487304873748738487394874348745487484875048761487634876548770
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 Iosco County
Iosco County shares a land border with 3 county equivalents. It has more land than 1 of them. The largest neighbor is Alcona County (674.7 mi²) and the smallest is Arenac County (363.2 mi²). Together with its neighbors, Iosco County forms a block of 2,150.8 mi² of land, of which it holds 25.5%.
| Bordering county equivalent | Land mi² | Size vs. Iosco | Compare |
|---|---|---|---|
| Alcona County | 674.7 | 1.2× larger | Compare |
| Ogemaw County | 563.5 | about the same | Compare |
| Arenac County | 363.2 | 1.5× smaller | Compare |
How big is Iosco County compared with U.S. states?
Iosco 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 Iosco 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 Iosco County?
Iosco County has more land than 1,322 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 Iosco County at #346 nationally by total area, 1,554 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 70.9%, compared with a national county-equivalent median of 1.2% — 69.8 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 Iosco County in the national ranking. They can be in different states and are not necessarily geographic neighbors.
| Land rank | County equivalent | Land mi² | Comparison |
|---|---|---|---|
| #1899 | Waukesha County, Wisconsin | 549.7 | Compare |
| #1900 | Iosco County, Michigan | 549.5 | This county |
| #1901 | Monroe County, Michigan | 549.4 | 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 44.386912, -83.380142. 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: 1,423,138,607 m²; AWATER: 3,472,103,966 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 Iosco County?
Iosco County, Michigan has 549.5 square miles (1,423.1 km²) of land and 1,340.6 square miles of water, for a total area of 1,890.1 square miles. It ranks #1900 of 3,222 U.S. county equivalents by land area.
Is Iosco County the largest county in Michigan?
No. Iosco County ranks #59 of 83 in Michigan by land area. The largest is Marquette County, with 1,809.1 square miles of land.
What counties border Iosco County?
Iosco County shares a land border with Alcona County, Ogemaw County, and Arenac County.
What is the population of Iosco County?
The Census Bureau estimates Iosco County had 25,266 residents on July 1, 2025, ranking #1,663 of 3,222 county equivalents. That is 46 people per square mile of land.
What is the county seat of Iosco County?
The county seat of Iosco County is Tawas City.
What cities and towns are in Iosco County?
Iosco County has 14 county subdivisions (cities, towns and townships). The most populous five are Oscoda charter township, Plainfield township, East Tawas city, Au Sable charter township, and Tawas City city.
Is Iosco County part of a metropolitan area?
No. Iosco County is outside every metropolitan and micropolitan statistical area in the July 2023 OMB delineation.
How many ZIP codes are in Iosco County?
12 ZIP Code Tabulation Areas have land in Iosco 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 Iosco 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 Iosco County?
The land measurement converts to approximately 351,665 acres. Including water, total area is approximately 1,209,641 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.