When was Jefferson County founded?

Jefferson County was founded in 1804, formed from Lycoming County and Westmoreland County, and named after Thomas Jefferson.

What is the county seat of Jefferson County?

The county seat of Jefferson County is Brookville.

Is there an online parcel map for Jefferson County?

Yes. North Central Pennsylvania Regional Planning & Development Commission (copy provided by Jefferson County GIS) publishes a parcel map of 33,556 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.

Has Jefferson County's boundary or name changed?

Jefferson County was created in 1804 from Lycoming County and Westmoreland County. Since then the Atlas of Historical County Boundaries records 7 later changes, chiefly involving Forest County, Elk. County and Indiana County.

Is my lot in a flood zone?

We do not have flood maps for Jefferson County yet. Look up the address on FEMA's Flood Map Service Center, which shows the effective flood map for any lot.

County · code 42065

Jefferson CountyPennsylvania

Jefferson County is a county in Pennsylvania with its seat in Brookville, formed on March 26, 1804. It was named after Thomas Jefferson.

Founded1804
County seatBrookville
Named forThomas Jefferson
Land area652 sq mi + 4.4 sq mi water
Population44,492 2020 Census
Parcels mapped33,556 checked 15 October 2026

Open the free map Click any parcel in Jefferson County: acreage, parcel id, address and who publishes the map. No sign-in.

Updated 19 October 2026

Census outline · seat marked

History

Formed in 1804 from Lycoming County and Westmoreland County

An old deed may name a county that no longer exists, or a boundary that has since moved.

Jefferson County was created on March 26, 1804, from Lycoming and Westmoreland Counties, initially unorganized and attached to Westmoreland. The county was fully organized on October 1, 1830, when it was detached from Indiana County. Jefferson County experienced boundary changes over the following decades, losing territory to create Elk County in 1843 and losing again to Elk County in 1868, while temporarily holding Forest County from 1848 to 1857.

Boundary changes from the Newberry Library, Atlas of Historical County Boundaries; the 5 that matter most are shown first.

1804
Jefferson County created Jefferson created from Lycoming; not fully organized, attached to Westmoreland.
from Lycoming from Westmoreland
26 March 1804 · Pa. Stat., ch. 2478, secs. 1, 13/pp. 769-770, 774
1843
Lost territory Jefferson lost to the creation of Elk.
to Elk.
18 April 1843 · Pa. Laws 1843, no. 150, sec. 1/p. 312
1848
Lost territory Jefferson lost to the creation of Forest; Forest attached to Jefferson.
to Forest
11 April 1848 · Pa. Laws 1851, res. 9/pp. 744-745
1850
Gained territory Jefferson gained from Forest.
from Forest
2 April 1850 · Pa. Laws 1850, no. 249, sec. 3/p. 315
1868
Gained territory Jefferson gained from Clearfield, lost to Elk.
from Clearfield from Elk.
4 April 1868 · Pa. Laws 1868, no. 611, sec. 1/pp. 651-652

Show all 8 changes (3 more)

1804
Jefferson County created Jefferson created from Lycoming; not fully organized, attached to Westmoreland.
from Lycoming from Westmoreland
26 March 1804 · Pa. Stat., ch. 2478, secs. 1, 13/pp. 769-770, 774
1806
Changed Jefferson detached from Westmoreland, attached to Indiana (but Jefferson remained indirectly attached to Westmoreland, through Indiana, until 3 Nov 1806).
Westmoreland Indiana
10 March 1806 · Pa. Stat., ch. 2665, sec. 9/18:123-124
1830
Changed Jefferson fully organized, detached from Indiana.
Indiana
1 October 1830 · Pa. Laws 1829-1830, no. 99, sec. 1/p. 161
1843
Lost territory Jefferson lost to the creation of Elk.
to Elk.
18 April 1843 · Pa. Laws 1843, no. 150, sec. 1/p. 312
1848
Lost territory Jefferson lost to the creation of Forest; Forest attached to Jefferson.
to Forest
11 April 1848 · Pa. Laws 1851, res. 9/pp. 744-745
1850
Gained territory Jefferson gained from Forest.
from Forest
2 April 1850 · Pa. Laws 1850, no. 249, sec. 3/p. 315
1857
Changed Forest detached from Jefferson.
Forest
1 September 1857 · Pa. Laws 1857, no. 653, secs. 1-2/pp. 612-613
1868
Gained territory Jefferson gained from Clearfield, lost to Elk.
from Clearfield from Elk.
4 April 1868 · Pa. Laws 1868, no. 611, sec. 1/pp. 651-652

Land and parcels

What the maps cover in Jefferson

Who publishes each layer, how good it is, and when we last checked.

Parcels Good enough

Lot lines and tax-map numbers for 33,556 parcels from North Central Pennsylvania Regional Planning & Development Commission (copy provided by Jefferson County GIS). Drawn for tax purposes: usually within a few feet of a survey, but not a survey.
edited 2 December 2025 · checked 15 October 2026
Address points Missing

No public address points layer found for Jefferson County yet.
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

Jefferson by the Census

Population

44,492 2020 Census count

Housing units

22,005 2020 Census count

Land area

652 square miles

Water area

4.4 square miles

People per sq mi

68 population ÷ land area

Source: US Census Bureau, 2020 Census; US Census Bureau, 2020 Gazetteer Files. Not endorsed or certified by the Census Bureau.

Rules and offices

Jefferson County's official site

We have found the county's site but not its offices yet; start there.

County government

County government
The official website of Jefferson County.
jeffersoncountypa.com

See your own lot on these maps

Open Jefferson 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.

Open the free map no sign-in Pro early access

Questions

Common questions about Jefferson County

When was Jefferson County founded?: Jefferson County was founded in 1804, formed from Lycoming County and Westmoreland County, and named after Thomas Jefferson.
What is the county seat of Jefferson County?: The county seat of Jefferson County is Brookville.
Is there an online parcel map for Jefferson County?: Yes. North Central Pennsylvania Regional Planning & Development Commission (copy provided by Jefferson County GIS) publishes a parcel map of 33,556 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.
Has Jefferson County's boundary or name changed?: Jefferson County was created in 1804 from Lycoming County and Westmoreland County. Since then the Atlas of Historical County Boundaries records 7 later changes, chiefly involving Forest County, Elk. County and Indiana County.
Is my lot in a flood zone?: We do not have flood maps for Jefferson County yet. Look up the address on FEMA's Flood Map Service Center, which shows the effective flood map for any lot.

Nearby