Bay County area

Population and density of Bay County

The Census Bureau estimates that 102,123 people lived in Bay County on July 1, 2025. That ranks #618 of 3,222 county equivalents nationally and #20 of 83 in Michigan. Since the April 1, 2020 estimates base of 103,863, the population has declined by 1,740 (−1.7%), compared with +0.5% for Michigan as a whole.

With 442.4 square miles of land, that is 231 people per square mile (89 per km²), placing Bay County #597 nationally for density and #15 in Michigan. The median county equivalent has 47 people per square mile; the Michigan median is 62. Put another way, there are about 2.8 acres of land per resident.

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 Bay County

Bay County is divided into 19 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 Bay City city, with 31,868 residents (31.2% of the county). The largest by land is Monitor charter township, at 36.8 mi², or 8.3% of the county’s land. Among those with at least 1,000 residents in 2020, Frankenlust township grew fastest since then (+0.4%).

Population: U.S. Census Bureau Vintage 2025 subcounty estimates, counting only the part of each subdivision inside Bay County. Land: 2026 Census Gazetteer. How communities are listed.

Metropolitan area

Bay County is a central county of the Bay City, MI Metropolitan Statistical Area. Bay County is the area’s only county equivalent, so the metro area has the same 442.4 square miles of land. By combined land it ranks #369 of 393 metropolitan areas, and #365 by population. It belongs to the Saginaw-Midland-Bay City, MI Combined Statistical Area.

ZIP codes

17 ZIP Code Tabulation Areas have land in Bay County; 10 of them have most of their land inside the county, and the others mainly cover neighboring areas.

4860448611486134862348631486344864248650486524865848659487064870848710487324874748757

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 Bay County

Bay County shares a land border with 5 county equivalents. It has more land than 1 of them. The largest neighbor is Tuscola County (804.9 mi²) and the smallest is Arenac County (363.2 mi²). Together with its neighbors, Bay County forms a block of 3,431.5 mi² of land, of which it holds 12.9%.

How big is Bay County compared with U.S. states?

Bay County has less land than any of the 50 states. Rhode Island, the smallest state by land area, has 1,033.9 mi², about 2.3 times as much. Michigan’s county land could hold about 128 areas the size of Bay County.

Another way to picture it: the same land area would fill a square about 21 miles (33.9 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 Bay County?

Bay County has more land than 925 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 Bay County at #1,640 nationally by total area, 657 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 29.9%, compared with a national county-equivalent median of 1.2% — 28.7 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 Bay County in the national ranking. They can be in different states and are not necessarily geographic neighbors.

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.