County · code 42085
Mercer CountyPennsylvania
Mercer County is a county in Pennsylvania with its seat in Mercer, formed on March 12, 1800. It was named after Hugh Mercer.
- Founded1800
- County seatMercer
- Named forHugh Mercer
- Land area673 sq mi + 10 sq mi water
- Population110,652 2020 Census
- Parcels mapped58,006 checked 14 October 2026
Where it is
Mercer on the map of Pennsylvania
Pennsylvania has 67 counties and county equivalents, each with its own records office. Shapes with a page are links.
History
Formed in 1800 from Allegheny County and Crawford County
An old deed may name a county that no longer exists, or a boundary that has since moved.
Mercer County was created on March 12, 1800 from Allegheny County and Crawford County, but was not fully organized at that time. It was fully organized and detached from Crawford on November 7, 1803, though it was reattached to Crawford on March 28, 1808. On September 1, 1849, Mercer County lost land to the creation of Lawrence County, but gained land from Crawford County on April 4, 1854.
- 1800Mercer County created Mercer created from Allegheny; not fully organized, attached to Crawford. · Pa. Stat., ch. 2130, pp. 455-456, 460-461
- 1803Changed Mercer fully organized, detached from Crawford · Pa. Stat., ch. 2391, sec. 1/17:480
- 1808
- 1849Lost territory Mercer lost to the creation of Lawrence. · Pa. Laws 1849, no. 366, secs. 1-2/pp. 551-552
- 1854
Land and parcels
What the maps cover in Mercer
Who publishes each layer, how good it is, and when we last checked.
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Parcels Good enough
Lot lines and tax-map numbers for 58,006 parcels from Mercer County. Drawn for tax purposes: usually within a few feet of a survey, but not a survey.
checked 14 October 2026 -
Address points Missing
No public address points layer found for Mercer County yet.
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Buildings Reference
Roof outlines traced from aerial imagery from FEMA Response Geospatial Office with Oak Ridge National Laboratory (ORNL). Good for seeing what is on a lot; not accurate enough to set a fence from.
checked 18 October 2026
- Official
- from the office that keeps the record
- Good enough
- a reliable statewide or national copy
- Fallback
- a guide only; check the official record
- Missing
- nothing public found yet
People and land
Mercer by the Census
Source: US Census Bureau, 2020 Census; US Census Bureau, 2020 Gazetteer Files. Not endorsed or certified by the Census Bureau.
Rules and offices
Who to ask before you build, dig or sell
Official county pages only. We link to them; we do not copy them, because they change.
Inside a city or town, permits usually come from that city rather than the county.
Permits
GIS and maps
County government
- County government
The official website of Mercer County.
See your own lot on these maps
Open Mercer County on Parcel Chart's free map and click your parcel. Save it with a free account; the full record of your place (site map, projects, documents) is Pro, in early access.
Questions
Common questions about Mercer County
- When was Mercer County founded?
- Mercer County was founded in 1800, formed from Allegheny County and Crawford County, and named after Hugh Mercer.
- What is the county seat of Mercer County?
- The county seat of Mercer County is Mercer.
- Is there an online parcel map for Mercer County?
- Yes. Mercer County publishes a parcel map of 58,006 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.
- Has Mercer County's boundary or name changed?
- Mercer County was created in 1800 from Allegheny County and Crawford County. Since then the Atlas of Historical County Boundaries records 4 later changes, chiefly involving Crawford County and Lawrence County.
- Who issues building permits in Mercer County?
- The county's page on building permits: License to Carry Permits. Inside a city or town, ask that city first.
- Is my lot in a flood zone?
- We do not have flood maps for Mercer County yet. Look up the address on FEMA's Flood Map Service Center, which shows the effective flood map for any lot.
Nearby