What is the county seat of Northumberland County?

The county seat of Northumberland County is Sunbury.

Is there an online parcel map for Northumberland County?

Yes. Northumberland County publishes a parcel map of 52,381 parcels, rated fallback here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.

Has Northumberland County's boundary or name changed?

Northumberland County was created in 1772 from Bedford County, Berks County, Cumberland County, Lancaster County and Northampton County. Since then the Atlas of Historical County Boundaries records 18 later changes, chiefly involving Litchfield (Conn.) County, Columbia County and Luzerne County.

Is my lot in a flood zone?

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

County · code 42097

Northumberland CountyPennsylvania

Northumberland County is in Pennsylvania and was created on March 21, 1772, with its seat in Sunbury.

Founded1772
County seatSunbury
Named forNorthumberland
Land area458 sq mi + 20 sq mi water
Population91,647 2020 Census
Parcels mapped52,381 checked 14 October 2026

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

Updated 19 October 2026

Census outline · seat marked

History

Formed in 1772 from Bedford County, Berks County, Cumberland County, Lancaster County and Northampton County

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

Northumberland County was formed from Bedford, Berks, Cumberland, Lancaster, and Northampton counties. The county lost significant territory over its early decades: parts went to Bedford in 1779, to Luzerne in 1786, to Allegheny in 1788, to Mifflin in 1789, and to Lycoming in 1795.

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

1772
Northumberland County created Northumberland created from Bedford, Berks, Cumberland, Lancaster, Northampton, and Non-County Area 1.
from Bedford from Berks from Cumberland from Lancaster from Northampton
21 March 1772 · Pa. Stat., ch. 644, sec. 1/8:143-144
1779
Lost territory Northumberland lost to Bedford.
to Bedford
30 September 1779 · Pa. Stat., ch. 848, sec. 1/9:396-398
1785
Gained territory Northumberland gained from Non-County Area 1; Non-County Area 1 eliminated. 8 April 1785 · Pa. Stat., ch. 1164, sec. 15/11:595
1786
Lost territory Northumberland lost to the creation of Luzerne.
to Luzerne
25 September 1786 · Pa. Stat., ch. 1244, sec. 1/12:300-301
1788
Lost territory Northumberland lost to the creation of Allegheny
to Allegheny
24 September 1788 · Pa. Stat., ch. 1359, sec. 1/13:84-85

Show all 22 changes (17 more)

1772
Northumberland County created Northumberland created from Bedford, Berks, Cumberland, Lancaster, Northampton, and Non-County Area 1.
from Bedford from Berks from Cumberland from Lancaster from Northampton
21 March 1772 · Pa. Stat., ch. 644, sec. 1/8:143-144
1774
Changed Northumberland overlapped by Litchfield (Connecticut), when Connecticut asserted its charter claim to northeastern Pennsylvania.
Litchfield (Conn.)
12 January 1774 · Cappon, Petchenik, and Long, 17, 92; Conn. Col. Recs., 13:427, 14:218
1775
Changed Northumberland's overlap by Litchfield (Connecticut) extended by Connecticut.
Litchfield (Conn.)
11 May 1775 · Cappon, Petchenik, and Long, 17, 92; Conn. Col. Recs., 15:13
1775
Changed Northumberland's overlap by Litchfield (Connecticut) reduced by Connecticut.
Litchfield (Conn.)
14 December 1775 · Cappon, Petchenik, and Long, 17, 92; Conn. Col. Recs., 15:197-198
1776
Changed Northumberland overlapped by Westmoreland (Connecticut), which replaced Litchfield (Connecticut)
Westmoreland (Conn.)Litchfield (Conn.)
10 October 1776 · Cappon, Petchenik, and Long, 17, 92; Conn. St. Recs., 1:7
1779
Lost territory Northumberland lost to Bedford.
to Bedford
30 September 1779 · Pa. Stat., ch. 848, sec. 1/9:396-398
1782
Changed Northumberland's overlap by Westmoreland (Connecticut) ended when Congress ruled in favor of Pennsylvania's claim to area.
Westmoreland (Conn.)
30 December 1782 · Susquehannah Co. Papers, 7:xxxiii, 245
1785
Gained territory Northumberland gained from Non-County Area 1; Non-County Area 1 eliminated. 8 April 1785 · Pa. Stat., ch. 1164, sec. 15/11:595
1786
Lost territory Northumberland lost to the creation of Luzerne.
to Luzerne
25 September 1786 · Pa. Stat., ch. 1244, sec. 1/12:300-301
1786
Boundary clarified Boundary between Northumberland and Luzerne redefined (no change).
with Luzerneno change
27 December 1786 · Pa. Stat., ch. 1256, sec. 8/12:343
1787
Boundary clarified Boundary between Northumberland and Luzerne redefined (no change).
with Luzerneno change
29 September 1787 · Pa. Stat., ch. 1323, sec. 3/12:588
1788
Lost territory Northumberland lost to the creation of Allegheny
to Allegheny
24 September 1788 · Pa. Stat., ch. 1359, sec. 1/13:84-85
1789
Lost territory Northumberland lost to the creation of Mifflin.
to Mifflin
19 September 1789 · Pa. Stat., ch. 1436, sec. 1/13:321-322
1795
Lost territory Northumberland lost to the creation of Lycoming.
to Lycoming
13 April 1795 · Pa. Stat., ch. 1834, sec. 1/15:288
1795
Boundary clarified Boundary between Northumberland and Berks clarified (no change).
with Berksno change
17 April 1795 · Pa. Stat., ch. 1848, sec. 1/15:312
1800
Lost territory Northumberland lost to the creation of Centre.
to Centre
13 February 1800 · Pa. Stat., ch. 2103, sec. 1/16:403
1808
Lost territory Northumberland lost to Luzerne.
to Luzerne
28 March 1808 · Pa. Stat., ch. 2988, sec. 1/18:887
1812
Lost territory Northumberland lost to Mifflin.
to Mifflin
20 March 1812 · Pa. Laws 1811-1812, ch. 96, sec. 1/p. 141
1813
Lost territory Northumberland lost to the creation of Columbia.
to Columbia
6 September 1813 · Pa. Laws 1812-1813, ch. 109, secs. 1-2/p. 146
1813
Lost territory Northumberland lost to the creation of Union.
to Union
1 November 1813 · Pa. Laws 1812-1813, ch. 110, secs. 1-2/p. 150
1815
Gained territory Northumberland gained from Columbia.
from Columbia
1 May 1815 · Pa. Laws 1814-1815, ch. 30, sec. 1/p. 38
1816
Lost territory Northumberland lost to Columbia.
to Columbia
1 May 1816 · Pa. Laws 1815-1816, ch. 9, sec. 1/pp. 6-7

Land and parcels

What the maps cover in Northumberland

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

Parcels Fallback

Lot lines and tax-map numbers for 52,381 parcels from Northumberland County. Drawn for tax purposes: usually within a few feet of a survey, but not a survey. This copy is a fallback, not the county's own: use it as a guide and check the official record.
edited 9 June 2021 · checked 14 October 2026
Address points Missing

No public address points layer found for Northumberland 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

Northumberland by the Census

Population

91,647 2020 Census count

Housing units

43,300 2020 Census count

Land area

458 square miles

Water area

20 square miles

People per sq mi

200 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

Northumberland 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 Northumberland County.
northumberlandco.org

See your own lot on these maps

Open Northumberland 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 Northumberland County

When was Northumberland County founded?: Northumberland County was founded in 1772, formed from Bedford County, Berks County, Cumberland County, Lancaster County and Northampton County, and named after Northumberland.
What is the county seat of Northumberland County?: The county seat of Northumberland County is Sunbury.
Is there an online parcel map for Northumberland County?: Yes. Northumberland County publishes a parcel map of 52,381 parcels, rated fallback here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.
Has Northumberland County's boundary or name changed?: Northumberland County was created in 1772 from Bedford County, Berks County, Cumberland County, Lancaster County and Northampton County. Since then the Atlas of Historical County Boundaries records 18 later changes, chiefly involving Litchfield (Conn.) County, Columbia County and Luzerne County.
Is my lot in a flood zone?: We do not have flood maps for Northumberland County yet. Look up the address on FEMA's Flood Map Service Center, which shows the effective flood map for any lot.

Nearby