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Mercer County, Illinois

Coordinates: 41°12′N 90°44′W / 41.20°N 90.74°W / 41.20; -90.74
From Wikipedia, the free encyclopedia

Mercer County, Illinois
County
Mercer County Courthouse
Mercer County Courthouse
Map of Illinois highlighting Mercer County
Location within the U.S. state of Illinois
Coordinates: 41°12′N 90°44′W / 41.2°N 90.74°W / 41.2; -90.74
Country United States
State Illinois
FoundedJanuary 13, 1825
Named afterHugh Mercer
SeatAledo
Largest cityAledo
Area
 • Total
569 sq mi (1,470 km2)
 • Land561 sq mi (1,450 km2)
 • Water7.5 sq mi (19 km2)  1.3%
Population
 (2020)
 • Total
15,699
 • Estimate 
(2024)
15,292 Decrease[1]
 • Density28.0/sq mi (10.8/km2)
Time zoneUTC−6 (Central)
 • Summer (DST)UTC−5 (CDT)
Congressional districts15th, 17th
Websitewww.mercercountyil.org

Mercer County is a county in Illinois. According to the 2020 census, it had a population of 15,699.[2] Its county seat is Aledo.[3] Mercer County is included in the Davenport-Moline-Rock Island, IA-IL Metropolitan Statistical Area.[4]

History

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Mercer County is named for Hugh Mercer (1726–1777), a physician and general during the American Revolution who died from wounds suffered at the Battle of Princeton.

In May 1812, Congress passed an act which set aside lands in Arkansas, Michigan, and Illinois as payment to volunteer soldiers in the War of 1812. Mercer County was part of this "Military Tract."

Seven years after Illinois became a state, Mercer County was founded. It was formed from unorganized territory near Pike County on January 13, 1825. Although the county had been created, its government was not organized for several years; for administration purposes it was attached first to Schuyler County (until 1826), then to Peoria (until 1831), and finally to Warren County. The organization of the county government was finally completed in 1835, after a large influx of settlers following the Black Hawk War.[5]

  • Mercer County at the time of its creation in 1825
    Mercer County at the time of its creation in 1825
  • Mercer County in 1827, reduced to its present borders
    Mercer County in 1827, reduced to its present borders

Geography

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According to the U.S. Census Bureau, the county has a total area of 569 square miles (1,470 km2), of which 561 square miles (1,450 km2) is land and 7.5 square miles (19 km2) (1.3%) is water.[6]

Climate and weather

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Aledo, Illinois
Climate chart (explanation)
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2.5
 
 
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█ Average max. and min. temperatures in °F
█ Precipitation totals in inches
Source: The Weather Channel[7]
Metric conversion
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1
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█ Average max. and min. temperatures in °C
█ Precipitation totals in mm

In recent years, average temperatures in the county seat of Aledo have ranged from a low of 11 °F (−12 °C) in January to a high of 84 °F (29 °C) in July, although a record low of −30 °F (−34 °C) was recorded in February 1905 and a record high of 113 °F (45 °C) was recorded in July 1936. Average monthly precipitation ranged from 1.27 inches (32 mm) in January to 4.43 inches (113 mm) in June.[7]

Major highways

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Adjacent counties

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Demographics

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Historical population
CensusPop.Note%±
183026—
18402,3528,946.2%
18505,246123.0%
186015,042186.7%
187018,76924.8%
188019,5023.9%
189018,545−4.9%
190020,94512.9%
191019,723−5.8%
192018,800−4.7%
193016,641−11.5%
194017,7016.4%
195017,374−1.8%
196017,149−1.3%
197017,2940.8%
198019,28611.5%
199017,290−10.3%
200016,957−1.9%
201016,434−3.1%
202015,699−4.5%
2024 (est.)15,292[8] Decrease−2.6%
U.S. Decennial Census[9]
1790-1960[10] 1900-1990[11]
1990-2000[12] 2010[13]

2020 census

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As of the 2020 census, the county had a population of 15,699. The median age was 45.1 years. 21.7% of residents were under the age of 18 and 22.3% of residents were 65 years of age or older. For every 100 females there were 100.4 males, and for every 100 females age 18 and over there were 99.6 males age 18 and over.[14][15]

The racial makeup of the county was 94.0% White, 0.5% Black or African American, 0.2% American Indian and Alaska Native, 0.2% Asian, <0.1% Native Hawaiian and Pacific Islander, 0.5% from some other race, and 4.5% from two or more races. Hispanic or Latino residents of any race comprised 3.0% of the population.[15]

<0.1% of residents lived in urban areas, while 100.0% lived in rural areas.[16]

There were 6,578 households in the county, of which 28.0% had children under the age of 18 living in them. Of all households, 54.2% were married-couple households, 18.1% were households with a male householder and no spouse or partner present, and 21.1% were households with a female householder and no spouse or partner present. About 27.7% of all households were made up of individuals and 14.1% had someone living alone who was 65 years of age or older.[14]

There were 7,291 housing units, of which 9.8% were vacant. Among occupied housing units, 80.2% were owner-occupied and 19.8% were renter-occupied. The homeowner vacancy rate was 2.4% and the rental vacancy rate was 9.7%.[14]

Racial and ethnic composition

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Mercer County, Illinois – Racial and ethnic composition
Note: the US Census treats Hispanic/Latino as an ethnic category. This table excludes Latinos from the racial categories and assigns them to a separate category. Hispanics/Latinos may be of any race.
Race / Ethnicity (NH = Non-Hispanic) Pop 1980[17] Pop 1990[18] Pop 2000[19] Pop 2010[20] Pop 2020[21] % 1980 % 1990 % 2000 % 2010 % 2020
White alone (NH) 19,096 17,082 16,551 15,912 14,578 99.01% 98.80% 97.61% 96.82% 92.86%
Black or African American alone (NH) 23 30 48 46 68 0.12% 0.17% 0.28% 0.28% 0.43%
Native American or Alaska Native alone (NH) 14 33 18 15 26 0.07% 0.19% 0.11% 0.09% 0.17%
Asian alone (NH) 19 35 29 51 37 0.10% 0.20% 0.17% 0.31% 0.24%
Native Hawaiian or Pacific Islander alone (NH) x [22] x [23] 1 1 2 x x 0.01% 0.01% 0.01%
Other race alone (NH) 19 1 5 6 17 0.10% 0.01% 0.03% 0.04% 0.11%
Mixed race or Multiracial (NH) x [24] x [25] 89 96 503 x x 0.52% 0.58% 3.20%
Hispanic or Latino (any race) 115 109 216 307 468 0.60% 0.63% 1.27% 1.87% 2.98%
Total 19,286 17,290 16,957 16,434 15,699 100.00% 100.00% 100.00% 100.00% 100.00%

2010 census

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As of the 2010 United States census, there were 16,434 people, 6,734 households, and 4,724 families residing in the county.[26] The population density was 29.3 inhabitants per square mile (11.3/km2). There were 7,358 housing units at an average density of 13.1 per square mile (5.1/km2).[6] The racial makeup of the county was 98.3% white, 0.3% black or African American, 0.3% Asian, 0.1% American Indian, 0.3% from other races, and 0.7% from two or more races. Those of Hispanic or Latino origin made up 1.9% of the population.[26] In terms of ancestry, 25.9% were German, 18.2% were Irish, 11.3% were English, 9.4% were Swedish, and 7.4% were American.[27]

Of the 6,734 households, 30.1% had children under the age of 18 living with them, 58.3% were married couples living together, 7.9% had a female householder with no husband present, 29.8% were non-families, and 25.8% of all households were made up of individuals. The average household size was 2.41 and the average family size was 2.88. The median age was 43.7 years.[26]

The median income for a household in the county was $50,909 and the median income for a family was $62,025. Males had a median income of $46,136 versus $30,392 for females. The per capita income for the county was $25,332. About 8.2% of families and 9.3% of the population were below the poverty line, including 14.9% of those under age 18 and 7.2% of those age 65 or over.[28]

Communities

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Cities

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Villages

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Census-designated place

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Unincorporated communities

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Townships

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Mercer County is divided into fifteen townships:

Politics

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Historically, Mercer County was a solidly Republican Yankee-influenced county, and before the Republican Party existed a stronghold of the Whig Party. The county never voted for a Democratic presidential candidate until Lyndon Johnson’s 1964 landslide over Barry Goldwater – the solitary break in Whig and Republican dominance occurring in 1912 when the GOP was mortally split and Progressive Theodore Roosevelt carried the county over conservative incumbent President William Howard Taft. After Johnson’s victory in the county, Mercer voted to being Republican between 1968 and 1984, but Reagan’s landslide in that election saw a swing to the Democrats that was capitalized upon by Michael Dukakis to carry the county in 1988. Between then and 2012, Mercer was solidly Democratic, but concern over declining economic opportunities in the “Rust Belt” caused a dramatic swing to populist Republican Donald Trump in 2016. Trump’s performance was the best by a Republican since Richard Nixon's 3,000-plus-county landslide in 1972.

Mercer County is located in Illinois's 17th Congressional District and is currently represented by Democrat Cheri Bustos. Within the Illinois House of Representatives, the county is located in the 74th district and is currently represented by Republican Daniel Swanson. The county is located in the 37th district of the Illinois Senate, and is currently represented by Republican Chuck Weaver.

United States presidential election results for Mercer County, Illinois[29]
Year Republican Democratic Third party(ies)
No.  % No.  % No.  %
1892 2,470 52.70% 1,975 42.14% 242 5.16%
1896 3,120 56.48% 2,329 42.16% 75 1.36%
1900 3,304 59.39% 2,110 37.93% 149 2.68%
1904 3,230 63.65% 1,386 27.31% 459 9.04%
1908 2,871 57.51% 1,777 35.60% 344 6.89%
1912 959 19.20% 1,602 32.07% 2,435 48.74%
1916 5,308 58.93% 3,430 38.08% 270 3.00%
1920 5,531 74.58% 1,574 21.22% 311 4.19%
1924 5,618 68.30% 1,699 20.66% 908 11.04%
1928 5,699 70.59% 2,316 28.69% 58 0.72%
1932 4,436 50.21% 4,309 48.77% 90 1.02%
1936 5,028 50.87% 4,751 48.07% 105 1.06%
1940 6,336 62.09% 3,830 37.53% 38 0.37%
1944 5,667 63.12% 3,277 36.50% 34 0.38%
1948 5,267 62.55% 3,117 37.02% 36 0.43%
1952 6,416 70.53% 2,679 29.45% 2 0.02%
1956 5,732 65.82% 2,969 34.10% 7 0.08%
1960 5,582 61.60% 3,476 38.36% 3 0.03%
1964 4,220 48.90% 4,410 51.10% 0 0.00%
1968 4,844 56.33% 3,143 36.55% 613 7.13%
1972 5,452 60.98% 3,477 38.89% 11 0.12%
1976 4,816 53.62% 4,090 45.54% 76 0.85%
1980 5,144 56.18% 3,361 36.71% 651 7.11%
1984 4,907 54.97% 3,982 44.61% 38 0.43%
1988 3,683 46.45% 4,204 53.02% 42 0.53%
1992 2,983 34.93% 3,990 46.72% 1,567 18.35%
1996 2,688 34.04% 4,278 54.17% 931 11.79%
2000 3,688 44.34% 4,400 52.90% 230 2.77%
2004 4,405 49.09% 4,512 50.28% 57 0.64%
2008 3,833 43.21% 4,887 55.10% 150 1.69%
2012 3,876 45.24% 4,507 52.60% 185 2.16%
2016 4,807 56.39% 3,071 36.02% 647 7.59%
2020 5,418 60.78% 3,280 36.80% 216 2.42%
2024 5,215 62.28% 2,950 35.23% 208 2.48%

See also

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Footnotes

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  1. ^ "County Population Totals and Components of Change: 2020–2024". United States Census Bureau. U.S. Department of Commerce. March 2025. Retrieved August 31, 2025.
  2. ^ "Mercer County, Illinois". United States Census Bureau. Retrieved June 10, 2023.
  3. ^ "Find a County". National Association of Counties. Retrieved June 7, 2011.
  4. ^ United States Office of Management and Budget. "Update of Statistical Area Definitions and Guidance on Their Uses" (PDF). pp. 5, 36. Archived from the original (PDF) on May 14, 2006. Retrieved July 21, 2006.
  5. ^ Mercer County Fact Sheet, Illinois State Archives. "Mercer County Fact Sheet". Archived from the original on October 23, 2007. Retrieved October 23, 2007.
  6. ^ a b "Population, Housing Units, Area, and Density: 2010 - County". United States Census Bureau. Retrieved July 12, 2015.{{cite web}}: CS1 maint: deprecated archival service (link)
  7. ^ a b "Monthly Averages for Aledo, Illinois". The Weather Channel. Retrieved January 27, 2011.
  8. ^ "Population and Housing Unit Estimates Tables". United States Census Bureau. Retrieved July 24, 2025.
  9. ^ "U.S. Decennial Census". United States Census Bureau. Retrieved July 7, 2014.
  10. ^ "Historical Census Browser". University of Virginia Library. Retrieved July 7, 2014.
  11. ^ "Population of Counties by Decennial Census: 1900 to 1990". United States Census Bureau. Retrieved July 7, 2014.
  12. ^ "Census 2000 PHC-T-4. Ranking Tables for Counties: 1990 and 2000" (PDF). United States Census Bureau. Retrieved July 7, 2014.
  13. ^ "QuickFacts". United States Census Bureau. Retrieved January 23, 2021.
  14. ^ a b c "2020 Decennial Census Demographic Profile (DP1)". United States Census Bureau. 2021. Retrieved December 25, 2025.
  15. ^ a b "2020 Decennial Census Redistricting Data (Public Law 94-171)". United States Census Bureau. 2021. Retrieved December 25, 2025.
  16. ^ "2020 Decennial Census Demographic and Housing Characteristics (DHC)". United States Census Bureau. 2023. Retrieved December 25, 2025.
  17. ^ "1980 Census of Population - General Population Characteristics - Illinois- Table 14 - Persons by Race and Table 16 (p. 18-28) - Total Persons and Spanish Origin Persons by Type of Spanish Origin and Race (p. 29-39)" (PDF). United States Census Bureau.
  18. ^ "1990 Census of Population - General Population Characteristics - Illinois - Table 6 - Race and Hispanic Orogin" (PDF). United States Census Bureau.
  19. ^ "P004: Hispanic or Latino, and Not Hispanic or Latino by Race – 2000: DEC Summary File 1 – Mercer County, Illinois". United States Census Bureau.
  20. ^ "P2: Hispanic or Latino, and Not Hispanic or Latino by Race – 2010: DEC Redistricting Data (PL 94-171) – Mercer County, Illinois". United States Census Bureau.
  21. ^ "P2: Hispanic or Latino, and Not Hispanic or Latino by Race – 2020: DEC Redistricting Data (PL 94-171) – Mercer County, Illinois". United States Census Bureau.
  22. ^ included in the Asian category in the 1980 Census
  23. ^ included in the Asian category in the 1990 Census
  24. ^ not an option in the 1980 Census
  25. ^ not an option in the 1990 Census
  26. ^ a b c "DP-1 Profile of General Population and Housing Characteristics: 2010 Demographic Profile Data". United States Census Bureau. Retrieved July 12, 2015.{{cite web}}: CS1 maint: deprecated archival service (link)
  27. ^ "DP02 SELECTED SOCIAL CHARACTERISTICS IN THE UNITED STATES – 2006-2010 American Community Survey 5-Year Estimates". United States Census Bureau. Retrieved July 12, 2015.{{cite web}}: CS1 maint: deprecated archival service (link)
  28. ^ "DP03 SELECTED ECONOMIC CHARACTERISTICS – 2006-2010 American Community Survey 5-Year Estimates". United States Census Bureau. Retrieved July 12, 2015.{{cite web}}: CS1 maint: deprecated archival service (link)
  29. ^ Leip, David. "Dave Leip's Atlas of U.S. Presidential Elections". uselectionatlas.org. Retrieved November 11, 2018.

Further reading

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41°12′N 90°44′W / 41.20°N 90.74°W / 41.20; -90.74

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