When was Mifflin County founded?

Mifflin County was founded in 1789, formed from Cumberland County and Northumberland County, and named after Thomas Mifflin.

What is the county seat of Mifflin County?

The county seat of Mifflin County is Lewistown.

Is there an online parcel map for Mifflin County?

Yes. Mifflin County publishes a parcel map of 24,545 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.

Has Mifflin County's boundary or name changed?

Mifflin County was created in 1789 from Cumberland County and Northumberland County. Since then the Atlas of Historical County Boundaries records 7 later changes, chiefly involving Huntingdon County, Centre County and Juniata County.

Is my lot in a flood zone?

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

County · code 42087

Mifflin CountyPennsylvania

Mifflin County is a county in Pennsylvania with its seat in Lewistown, formed in 1789. The county was named after Thomas Mifflin.

Founded1789
County seatLewistown
Named forThomas Mifflin
Land area411 sq mi + 3.7 sq mi water
Population46,143 2020 Census
Parcels mapped24,545 checked 15 October 2026

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

Updated 19 October 2026

Census outline · seat marked

History

Formed in 1789 from Cumberland County and Northumberland County

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

Mifflin County was created on September 19, 1789, from Cumberland County and Northumberland County. Over the following decades, the county gained and lost territory through multiple boundary adjustments, including the creation of Centre County in 1800, Union County in 1819, and Juniata County in 1831.

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

1789
Mifflin County created Mifflin created from Cumberland and Northumberland.
from Cumberland from Northumberland
19 September 1789 · Pa. Stat., ch. 1436, sec. 1/13:321-322
1792
Gained territory Mifflin gained from Huntingdon.
from Huntingdon
29 March 1792 · Pa. Stat., ch. 1617, sec. 1/14:219-220
1800
Lost territory Mifflin lost to the creation of Centre.
to Centre
13 February 1800 · Pa. Stat., ch. 2103, sec. 1/16:403
1812
Gained territory Mifflin gained from Northumberland.
from Northumberland
20 March 1812 · Pa. Laws 1811-1812, ch. 96, sec. 1/p. 141
1812
Lost territory Mifflin lost to Huntingdon.
to Huntingdon
30 March 1812 · Pa. Laws 1811-1812, ch. 141, sec. 1/pp. 195-196

Show all 10 changes (5 more)

1789
Mifflin County created Mifflin created from Cumberland and Northumberland.
from Cumberland from Northumberland
19 September 1789 · Pa. Stat., ch. 1436, sec. 1/13:321-322
1791
Boundary clarified Boundary between Mifflin and Huntingdon clarified (no change).
with Huntingdonno change
1 April 1791 · Pa. Stat., ch. 1544, sec. 1/14:46-47
1792
Gained territory Mifflin gained from Huntingdon.
from Huntingdon
29 March 1792 · Pa. Stat., ch. 1617, sec. 1/14:219-220
1800
Lost territory Mifflin lost to the creation of Centre.
to Centre
13 February 1800 · Pa. Stat., ch. 2103, sec. 1/16:403
1812
Gained territory Mifflin gained from Northumberland.
from Northumberland
20 March 1812 · Pa. Laws 1811-1812, ch. 96, sec. 1/p. 141
1812
Lost territory Mifflin lost to Huntingdon.
to Huntingdon
30 March 1812 · Pa. Laws 1811-1812, ch. 141, sec. 1/pp. 195-196
1819
Lost territory Mifflin lost to Union.
to Union
16 March 1819 · Pa. Laws 1818-1819, ch. 77, sec. 1/pp. 111-112
1831
Lost territory Mifflin lost to the creation of Juniata.
to Juniata
1 September 1831 · Pa. Laws 1830-1831, no. 67, secs. 1-2/pp. 99-100
1834
Gained territory Mifflin gained from Huntingdon.
from Huntingdon
15 April 1834 · Pa. Laws 1833-1834, no. 227, sec. 1/p. 503
1855
Boundary clarified Boundary between Mifflin and Huntingdon clarified (no change).
with Huntingdonno change
27 April 1855 · Pa. Laws 1855, no. 357, sec. 1/p. 343

Land and parcels

What the maps cover in Mifflin

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

Parcels Good enough

Lot lines and tax-map numbers for 24,545 parcels from Mifflin County. Drawn for tax purposes: usually within a few feet of a survey, but not a survey.
checked 15 October 2026
Address points Missing

No public address points layer found for Mifflin 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

Mifflin by the Census

Population

46,143 2020 Census count

Housing units

21,313 2020 Census count

Land area

411 square miles

Water area

3.7 square miles

People per sq mi

112 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

Mifflin 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 Mifflin County.
co.mifflin.pa.us

See your own lot on these maps

Open Mifflin 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 Mifflin County

When was Mifflin County founded?: Mifflin County was founded in 1789, formed from Cumberland County and Northumberland County, and named after Thomas Mifflin.
What is the county seat of Mifflin County?: The county seat of Mifflin County is Lewistown.
Is there an online parcel map for Mifflin County?: Yes. Mifflin County publishes a parcel map of 24,545 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.
Has Mifflin County's boundary or name changed?: Mifflin County was created in 1789 from Cumberland County and Northumberland County. Since then the Atlas of Historical County Boundaries records 7 later changes, chiefly involving Huntingdon County, Centre County and Juniata County.
Is my lot in a flood zone?: We do not have flood maps for Mifflin County yet. Look up the address on FEMA's Flood Map Service Center, which shows the effective flood map for any lot.

Nearby