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Mercer County, Missouri facts for kids

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Mercer County
Mercer County Courthouse in downtown Princeton
Mercer County Courthouse in downtown Princeton
Map of Missouri highlighting Mercer County
Location within the U.S. state of Missouri
Map of the United States highlighting Missouri
Missouri's location within the U.S.
Country  United States
State  Missouri
Founded February 14, 1845
Named for John Francis Mercer
Seat Princeton
Largest city Princeton
 • Total 455 sq mi (1,180 km2)
 • Land 454 sq mi (1,180 km2)
 • Water 1.3 sq mi (3 km2)  0.3%
 • Total 3,538
 • Estimate 
 • Density 7.776/sq mi (3.002/km2)
Time zone UTC−6 (Central)
 • Summer (DST) UTC−5 (CDT)
Congressional district 6th

Mercer County is a county located in the northwestern portion of the U.S. state of Missouri. As of the 2020 census, the population was 3,538. making it the second-least populous county in Missouri. Its county seat is Princeton. The county was organized February 14, 1845 and named for General John F. Mercer of the Revolutionary War.


Early years

Mercer County was organized February 14, 1845, from part of Grundy County, Missouri. It is named in honor of General John Francis Mercer who fought and died in the American Revolutionary War. The first permanent settlements in what is now Mercer County were in 1837 when a few families from other parts of Missouri moved to the area. James Parsons, a Tennessee native, is generally considered to be the first permanent settler in the spring of 1837. The land was still included as part of Livingston County at that time and would remain so until 1841 when it would become part of the newly created Grundy County. Prior to 1837, the land was used by Native American tribes, primarily the Sac/Fox and Potawatomi, as prime hunting grounds. The occasional temporary hunting village would be established by the tribes but otherwise the land was devoid of humans. The town of Princeton, named for the battle where General Mercer was killed, was established as the county seat in 1847. The northern boundary of the county was in dispute for the first six years of its existence due to the Honey War, a bloodless territorial dispute between Missouri and Iowa. The boundary was 9.5 miles farther north than present day prior to an 1851 decision by the U.S. Supreme Court.

Civil War

Mercer County, like its neighbor to the east Putnam County, was a staunch supporter of the Union. Most county residents had roots in northern U.S. states "back east" like Pennsylvania, Ohio, and Indiana, and didn't have the strong slave-holding tradition of other northern Missouri counties like Macon, Audrain, and Monroe (commonly referred to as Little Dixie) whose population largely emigrated from Southern states. In the 1860 U.S. Census, only 12 Mercer County families were listed as slave owners, with a combined total of 24 slaves. Fewer than 20 Mercer County men fought for the Confederacy, while well over 1,000 volunteered for Union service. Among the units containing men from Mercer County were the Twenty-Third, Twenty-Seventh and Thirty-Fifth Regiments, the Second and Twelfth Cavalry, the Fifth Kansas Cavalry, and various smaller units of the Missouri State Militia.


According to the U.S. Census Bureau, the county has a total area of 455 square miles (1,180 km2), of which 454 square miles (1,180 km2) is land and 1.3 square miles (3.4 km2) (0.3%) is water.

Adjacent counties

Major highways

  • US 65.svg U.S. Route 65
  • US 136.svg U.S. Route 136


Historical population
Census Pop.
1850 2,691
1860 9,300 245.6%
1870 11,557 24.3%
1880 14,673 27.0%
1890 14,581 −0.6%
1900 14,706 0.9%
1910 12,335 −16.1%
1920 11,281 −8.5%
1930 9,350 −17.1%
1940 8,766 −6.2%
1950 7,235 −17.5%
1960 5,750 −20.5%
1970 4,910 −14.6%
1980 4,685 −4.6%
1990 3,723 −20.5%
2000 3,757 0.9%
2010 3,785 0.7%
2020 3,538 −6.5%
U.S. Decennial Census
1790-1960 1900-1990
1990-2000 2010-2015

As of the census of 2010, there were 3,785 people, 1,600 households, and 1,089 families residing in the county. The population density was 8 people per square mile (3/km2). There were 2,125 housing units at an average density of 5 per square mile (2/km2). The racial makeup of the county was 98.72% White, 0.19% Black or African American, 0.56% Native American, 0.05% Pacific Islander, 0.03% from other races, and 0.45% from two or more races. Approximately 0.29% of the population were Hispanic or Latino of any race.

There were 1,600 households, out of which 28.30% had children under the age of 18 living with them, 57.60% were married couples living together, 6.70% had a female householder with no husband present, and 31.90% were non-families. 29.30% of all households were made up of individuals, and 17.60% had someone living alone who was 65 years of age or older. The average household size was 2.31 and the average family size was 2.83.

In the county, the population was spread out, with 23.00% under the age of 18, 6.70% from 18 to 24, 24.20% from 25 to 44, 24.00% from 45 to 64, and 22.00% who were 65 years of age or older. The median age was 42 years. For every 100 females there were 95.70 males. For every 100 females age 18 and over, there were 92.60 males.

The median income for a household in the county was $29,640, and the median income for a family was $35,313. Males had a median income of $26,690 versus $19,814 for females. The per capita income for the county was $15,140. About 10.20% of families and 13.30% of the population were below the poverty line, including 13.30% of those under age 18 and 14.50% of those age 65 or over.




Census-designated place

Other communities

Historical communities


  • Adel 40°31′53″N 93°40′08″W / 40.53139°N 93.66889°W / 40.53139; -93.66889 (Adel, Missouri)
  • Alvord 40°27′20″N 93°35′43″W / 40.45556°N 93.59528°W / 40.45556; -93.59528 (Alvord, Missouri)
  • Burrows 40°30′58″N 93°45′20″W / 40.51611°N 93.75556°W / 40.51611; -93.75556 (Burrows, Missouri)
  • Cleopatra 40°32′55″N 93°24′15″W / 40.54861°N 93.40417°W / 40.54861; -93.40417 (Cleopatra, Missouri)
  • Dinsmore 40°20′28″N 93°44′41″W / 40.34111°N 93.74472°W / 40.34111; -93.74472 (Dinsmore, Missouri)
  • Goshen 40°22′58″N 93°40′46″W / 40.38278°N 93.67944°W / 40.38278; -93.67944 (Goshen, Missouri)
  • Half Rock 40°16′23″N 93°26′08″W / 40.27306°N 93.43556°W / 40.27306; -93.43556 (Half Rock (Mercer County), Missouri)
  • Ilia 40°31′50″N 93°27′01″W / 40.53056°N 93.45028°W / 40.53056; -93.45028 (Ilia, Missouri)
  • Saline 40°31′37″N 93°43′40″W / 40.52694°N 93.72778°W / 40.52694; -93.72778 (Saline (Mercer County), Missouri)
  • Topsy (Newtown) 40°21′11″N 93°28′47″W / 40.35306°N 93.47972°W / 40.35306; -93.47972 (Topsy (Newtown), Missouri)
  • Wataga 40°33′38″N 93°37′59″W / 40.56056°N 93.63306°W / 40.56056; -93.63306 (Wataga, Missouri)



  • Harrison
  • Lindley
  • Madison
  • Marion
  • Medicine
  • Morgan
  • Ravanna
  • Somerset
  • Washington


    • North Mercer County Elementary School (PK-06)
    • Mercer High School (07-12)
    • Princeton Elementary School (PK-06)
    • Princeton High School (07-12)

Public libraries

  • Mercer County Library
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