County outline
Where Mercer County is located
Area breakdown
Land accounts for 98.5% of Mercer County’s measured area and water for 1.5%. Its combined area converts to 1,767.8 square kilometers or approximately 436,840 acres.
Green: land · blue: water
| Measurement | Square miles | Square kilometers | Acres |
|---|---|---|---|
| Land | 672.538 | 1,741.865 | 430,424.3 |
| Water | 10.025 | 25.965 | 6,416 |
| Total | 682.563 | 1,767.83 | 436,840.3 |
How Mercer County compares
By original Census land area, Mercer County ranks #33 of 67 in Pennsylvania and #1402 of 3,222 nationally. National rankings include the 50 states, District of Columbia, and Puerto Rico.
Its land area is 1.029 times the Pennsylvania county-equivalent median of 653.3 square miles. It accounts for 1.5% of the combined county land area in the state.
See the complete Pennsylvania ranking · What counts as a county equivalent?
Population and density of Mercer County
The Census Bureau estimates that 107,860 people lived in Mercer County on July 1, 2025. That ranks #590 of 3,222 county equivalents nationally and #30 of 67 in Pennsylvania. Since the April 1, 2020 estimates base of 110,661, the population has declined by 2,801 (−2.5%), compared with +0.4% for Pennsylvania as a whole.
With 672.5 square miles of land, that is 160 people per square mile (62 per km²), placing Mercer County #744 nationally for density and #31 in Pennsylvania. The median county equivalent has 47 people per square mile; the Pennsylvania median is 137. Put another way, there are about 4 acres of land per resident.
| July 1 | 2020 | 2021 | 2022 | 2023 | 2024 | 2025 |
|---|---|---|---|---|---|---|
| Estimate | 110,553 | 110,002 | 109,142 | 108,556 | 108,238 | 107,860 |
| Change | — | −551 | −860 | −586 | −318 | −378 |
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 Mercer County
Mercer County is divided into 47 municipalities and townships. In Pennsylvania, county subdivisions are local governments, and together they cover all of the county’s land and residents.
The most populous is Hermitage city, with 16,308 residents (15.1% of the county). The largest by land is West Salem township, at 36.9 mi², or 5.5% of the county’s land. The county seat, Mercer borough, has 1,905 residents. Among those with at least 1,000 residents in 2020, Liberty township grew fastest since then (+3.9%).
| County subdivision | Population 2025 | Since 2020 | Land mi² | Share of county land |
|---|---|---|---|---|
| Hermitage city | 16,308 | −3% | 30.3 | 4.5% |
| Sharon city | 12,648 | −3.8% | 3.772 | 0.6% |
| Grove City borough | 7,694 | −2.1% | 2.682 | 0.4% |
| Greenville borough | 5,406 | −2.2% | 1.887 | 0.3% |
| Pine township | 4,730 | −1.9% | 25.4 | 3.8% |
| Farrell city | 4,110 | −3.5% | 2.264 | 0.3% |
| Sharpsville borough | 4,095 | −3.7% | 1.391 | 0.2% |
| Hempfield township | 3,646 | −2.8% | 14.2 | 2.1% |
| Shenango township | 3,431 | −2.9% | 30 | 4.5% |
| West Salem township | 3,177 | −1.3% | 36.9 | 5.5% |
| Pymatuning township | 3,031 | −3.2% | 16.2 | 2.4% |
| Findley township | 2,827 | −0.7% | 21.2 | 3.2% |
| South Pymatuning township | 2,566 | −3.4% | 19.6 | 2.9% |
| Lackawannock township | 2,465 | −0.6% | 20.9 | 3.1% |
| Coolspring township | 2,076 | −1.8% | 18.8 | 2.8% |
Show the other 32 subdivisions
| Name | Population 2025 | Since 2020 | Land mi² |
|---|---|---|---|
| Delaware township | 2,022 | −1.9% | 32.7 |
| Mercer boroughCounty seat | 1,905 | −3.8% | 1.157 |
| Jefferson township | 1,853 | −3.6% | 24.7 |
| Springfield township | 1,822 | −1.7% | 27.3 |
| East Lackawannock township | 1,635 | −1.9% | 21.4 |
| Liberty township | 1,468 | +3.9% | 14.8 |
| Wilmington township | 1,416 | +0.4% | 13.1 |
| Perry township | 1,297 | −2.8% | 18 |
| Jackson township | 1,195 | +0.7% | 17.5 |
| Sandy Lake township | 1,187 | −1% | 24.4 |
| Greene township | 1,032 | −2% | 21.8 |
| Fairview township | 931 | −2.1% | 18.5 |
| Stoneboro borough | 922 | −2.6% | 2.834 |
| Sugar Grove township | 917 | −3.7% | 12.4 |
| Worth township | 800 | −2.9% | 24.7 |
| West Middlesex borough | 772 | −3.6% | 0.845 |
| Sandy Creek township | 766 | −2.3% | 15.8 |
| Mill Creek township | 757 | −2.3% | 19 |
| Salem township | 744 | −2.5% | 13.4 |
| French Creek township | 705 | −0.7% | 20.7 |
| Wolf Creek township | 700 | −2% | 16.9 |
| Lake township | 682 | −2.7% | 16.4 |
| Sandy Lake borough | 624 | −3.7% | 0.832 |
| Clark borough | 558 | −3.5% | 3.011 |
| Jamestown borough | 556 | −3.5% | 0.833 |
| Otter Creek township | 509 | −3% | 11.8 |
| New Vernon township | 481 | −2.2% | 14.9 |
| Deer Creek township | 448 | −3.4% | 14.5 |
| Fredonia borough | 417 | −3.9% | 0.357 |
| New Lebanon borough | 195 | +4.8% | 1.273 |
| Jackson Center borough | 189 | −3.6% | 1.138 |
| Sheakleyville borough | 145 | −3.3% | 0.196 |
Population: U.S. Census Bureau Vintage 2025 subcounty estimates, counting only the part of each subdivision inside Mercer County. Land: 2026 Census Gazetteer. How communities are listed.
Metropolitan area
Mercer County is a central county of the Hermitage, PA Micropolitan Statistical Area. Mercer County is the area’s only county equivalent, so the micro area has the same 672.5 square miles of land. By combined land it ranks #322 of 542 micropolitan areas, and #24 by population. It belongs to the Pittsburgh-Weirton-Steubenville, PA-OH-WV Combined Statistical Area.
ZIP codes
28 ZIP Code Tabulation Areas have land in Mercer County; 20 of them have most of their land inside the county, and the others mainly cover neighboring areas.
16057161101611316114161211612416125161271613016133161341613716142161431614516146161481615016151161531615416156161591616116311163141634216362
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 Mercer County
Mercer County shares a land border with 6 county equivalents, including 2 in Ohio. It has more land than 3 of them. The largest neighbor is Crawford County (1,012.4 mi²) and the smallest is Lawrence County (357.4 mi²). Together with its neighbors, Mercer County forms a block of 4,535.1 mi² of land, of which it holds 14.8%.
| Bordering county equivalent | Land mi² | Size vs. Mercer | Compare |
|---|---|---|---|
| Crawford County | 1,012.4 | 1.5× larger | Compare |
| Butler County | 789.5 | 1.2× larger | Compare |
| Venango County | 674.3 | about the same | Compare |
| Trumbull CountyOhio | 617.6 | 1.1× smaller | Compare |
| Mahoning CountyOhio | 411.5 | 1.6× smaller | Compare |
| Lawrence County | 357.4 | 1.9× smaller | Compare |
How big is Mercer County compared with U.S. states?
Mercer County has less land than any of the 50 states. Rhode Island, the smallest state by land area, has 1,033.9 mi², about 1.5 times as much. Pennsylvania’s county land could hold about 67 areas the size of Mercer County.
Another way to picture it: the same land area would fill a square about 25.9 miles (41.7 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 Mercer County?
Mercer County has more land than 1,820 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 Mercer County at #1,485 nationally by total area, 83 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 1.5%, compared with a national county-equivalent median of 1.2% — 0.3 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 Mercer County in the national ranking. They can be in different states and are not necessarily geographic neighbors.
| Land rank | County equivalent | Land mi² | Comparison |
|---|---|---|---|
| #1401 | Sequoyah County, Oklahoma | 673.6 | Compare |
| #1402 | Mercer County, Pennsylvania | 672.5 | This county |
| #1403 | Pike County, Alabama | 672.1 | 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 41.300014, -80.252786. 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: 1,741,866,425 m²; AWATER: 25,964,035 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 Mercer County?
Mercer County, Pennsylvania has 672.5 square miles (1,741.9 km²) of land and 10 square miles of water, for a total area of 682.6 square miles. It ranks #1402 of 3,222 U.S. county equivalents by land area.
Is Mercer County the largest county in Pennsylvania?
No. Mercer County ranks #33 of 67 in Pennsylvania by land area. The largest is Lycoming County, with 1,228.9 square miles of land.
What counties border Mercer County?
Mercer County shares a land border with Crawford County, Trumbull County, Ohio, Lawrence County, Venango County, Butler County, and Mahoning County, Ohio.
What is the population of Mercer County?
The Census Bureau estimates Mercer County had 107,860 residents on July 1, 2025, ranking #590 of 3,222 county equivalents. That is 160 people per square mile of land.
What is the county seat of Mercer County?
The county seat of Mercer County is Mercer.
What cities and towns are in Mercer County?
Mercer County has 47 county subdivisions (cities, towns and townships). The most populous five are Hermitage city, Sharon city, Grove City borough, Greenville borough, and Pine township.
Is Mercer County part of a metropolitan area?
Yes. It is a central county of the Hermitage, PA Micropolitan Statistical Area.
How many ZIP codes are in Mercer County?
28 ZIP Code Tabulation Areas have land in Mercer County, and 20 of them have most of their land inside the county. Census ZIP Code Tabulation Areas approximate USPS ZIP Code areas.
How does Mercer County compare with U.S. states?
It has less land than every state. Rhode Island, the smallest, has 1.5 times as much land.
How many acres of land are in Mercer County?
The land measurement converts to approximately 430,424 acres. Including water, total area is approximately 436,840 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.