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County · code 29129

Mercer CountyMissouri

Mercer County is a county in northern Missouri with its county seat in Princeton. The county was established in 1843 and is named after John Francis Mercer.

  • Founded1843
  • County seatPrinceton
  • Named forJohn Francis Mercer
  • Land area454 sq mi + 1.3 sq mi water
  • Population3,538 2020 Census
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Updated

GrundyDecatur, IAHarrisonPutnam Princeton Census outline · seat marked

Where it is

Mercer on the map of Missouri

Missouri has 115 counties and county equivalents, each with its own records office. Shapes with a page are links.

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Counties of Missouri · Mercer highlighted

History

Formed in 1843 from Grundy County

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

Mercer County was created from Non-County Area 18 on February 22, 1843, but was not fully organized until 1845, when it was detached from Grundy County. In 1849, the U.S. Supreme Court settled a boundary dispute between Missouri and Iowa by establishing the Indian boundary line run and marked by John C. Sullivan in 1816 as the state boundary.

Boundary changes from the Newberry Library, Atlas of Historical County Boundaries.

  1. 1843
    Mercer County created Mercer created from Non-County Area 18; Mercer not fully organized, attached to Grundy "for civil and military purposes." Non-County Area 18 eliminated.
    from Grundy
    · Mo. Laws 1842-1843, pub., p. 37
  2. 1845
    Changed Mercer fully organized, detached from Grundy.
    Grundy
    · Mo. Laws 1844-1845, secs. 21, 41/pp. 33-34, 36
  3. 1849
    Changed U.S. Supreme Court settled boundary dispute between Missouri and Iowa, dating from 11 February 1839, by rejecting both states' claims, choosing instead the Indian boundary line run and marked by John C. Sullivan in 1816 (the commonly accepted boundary before the dispute arose and the present boundary between the two states). The decision ended Mercer's claim to territory in the state of Iowa (no change).
    U.s.
    · Landers, 647-648; Thomas, 269-270

Land and parcels

What the maps cover in Mercer

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

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

Population
3,538 2020 Census count
Housing units
1,911 2020 Census count
Land area
454 square miles
Water area
1.3 square miles
People per sq mi
8 population ÷ land area

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

See your own lot on these maps

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Questions

Common questions about Mercer County

When was Mercer County founded?
Mercer County was founded in 1843, formed from Grundy County, and named after John Francis Mercer.
What is the county seat of Mercer County?
The county seat of Mercer County is Princeton.
Is there an online parcel map for Mercer County?
Not that we have found yet. Lot lines and owners of record are kept by the county assessor's office. When a public parcel map appears, it shows here.
Has Mercer County's boundary or name changed?
Mercer County was created in 1843 from Grundy County. Since then the Atlas of Historical County Boundaries records 1 later change, chiefly involving Grundy County.
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

Counties next door