Mercer County, Illinois | |
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 Location within the U.S. state ofIllinois | |
 Illinois's location within theU.S. | |
| Coordinates:41°12′N90°44′W / 41.2°N 90.74°W /41.2; -90.74 | |
| Country |  United States |
| State |  Illinois |
| Founded | January 13, 1825 |
| Named after | Hugh Mercer |
| Seat | Aledo |
| Largest city | Aledo |
| Area | |
• Total | 569 sq mi (1,470 km2) |
| • Land | 561 sq mi (1,450 km2) |
| • Water | 7.5 sq mi (19 km2) 1.3% |
| Population (2020) | |
• Total | 15,699 |
• Estimate (2024) | 15,292 [1] |
| • Density | 28.0/sq mi (10.8/km2) |
| Time zone | UTC−6 (Central) |
| • Summer (DST) | UTC−5 (CDT) |
| Congressional districts | 15th,17th |
| Website | www |
Mercer County is acounty inIllinois. According to the2020 census, it had a population of 15,699.[2] Itscounty seat isAledo.[3] Mercer County is included in theDavenport-Moline-Rock Island, IA-ILMetropolitan Statistical Area.[4]
Mercer County is named forHugh Mercer (1726–1777), a physician and general during theAmerican Revolution who died from wounds suffered at theBattle of Princeton.
In May 1812, Congress passed an act which set aside lands inArkansas,Michigan, and Illinois as payment to volunteer soldiers in theWar 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 nearPike 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 theBlack Hawk War.[5]
According to theU.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]
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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]
| Census | Pop. | Note | %± |
|---|---|---|---|
| 1830 | 26 | — | |
| 1840 | 2,352 | 8,946.2% | |
| 1850 | 5,246 | 123.0% | |
| 1860 | 15,042 | 186.7% | |
| 1870 | 18,769 | 24.8% | |
| 1880 | 19,502 | 3.9% | |
| 1890 | 18,545 | −4.9% | |
| 1900 | 20,945 | 12.9% | |
| 1910 | 19,723 | −5.8% | |
| 1920 | 18,800 | −4.7% | |
| 1930 | 16,641 | −11.5% | |
| 1940 | 17,701 | 6.4% | |
| 1950 | 17,374 | −1.8% | |
| 1960 | 17,149 | −1.3% | |
| 1970 | 17,294 | 0.8% | |
| 1980 | 19,286 | 11.5% | |
| 1990 | 17,290 | −10.3% | |
| 2000 | 16,957 | −1.9% | |
| 2010 | 16,434 | −3.1% | |
| 2020 | 15,699 | −4.5% | |
| 2024 (est.) | 15,292 | [8] | −2.6% |
| U.S. Decennial Census[9] 1790-1960[10] 1900-1990[11] 1990-2000[12] 2010[13] | |||
| Race / Ethnicity(NH = Non-Hispanic) | Pop 1980[14] | Pop 1990[15] | Pop 2000[16] | Pop 2010[17] | Pop 2020[18] | % 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 orAlaska 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 orPacific Islander alone (NH) | x[19] | x[20] | 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[21] | x[22] | 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% |
As of the2010 United States census, there were 16,434 people, 6,734 households, and 4,724 families residing in the county.[23] 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.[23] In terms of ancestry, 25.9% wereGerman, 18.2% wereIrish, 11.3% wereEnglish, 9.4% wereSwedish, and 7.4% wereAmerican.[24]
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.[23]
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 thepoverty line, including 14.9% of those under age 18 and 7.2% of those age 65 or over.[25]
Mercer County is divided into fifteentownships:
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Historically, Mercer County was a solidly Republican Yankee-influenced county, and before the Republican Party existed a stronghold of theWhig Party. The county never voted for a Democratic presidential candidate untilLyndon Johnson’s 1964 landslide overBarry Goldwater – the solitary break in Whig and Republican dominance occurring in 1912 when the GOP was mortally split andProgressiveTheodore Roosevelt carried the county over conservative incumbent PresidentWilliam Howard Taft. After Johnson’s victory in the county, Mercer voted to being Republican between 1968 and 1984, butReagan’s landslide in that election saw a swing to the Democrats that was capitalized upon byMichael 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 RepublicanDonald Trump in 2016. Trump’s performance was the best by a Republican sinceRichard Nixon's 3,000-plus-county landslide in 1972.
Mercer County is located inIllinois's 17th Congressional District and is currently represented by DemocratCheri Bustos. Within theIllinois House of Representatives, the county is located in the 74th district and is currently represented by RepublicanDaniel Swanson. The county is located in the 37th district of theIllinois Senate, and is currently represented by RepublicanChuck Weaver.
| 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% |
Places adjacent to Mercer County, Illinois | |
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Municipalities and communities ofMercer County, Illinois,United States | ||
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| Other communities | ||
| Footnotes | ‡This populated place also has portions in an adjacent county or counties | |
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