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Jefferson County, Illinois

Jefferson County, Illinois
Jefferson County Courthouse in Mount Vernon
Map of Illinois highlighting Jefferson County
Location in the state of Illinois
Map of the United States highlighting Illinois
Illinois's location in the U.S.
Founded 1819
Named for Thomas Jefferson
Seat Mount Vernon
Largest city Mount Vernon
 • Total 584 sq mi (1,513 km2)
 • Land 571 sq mi (1,479 km2)
 • Water 13 sq mi (34 km2), 2.2%
 • (2010) 38,827
 • Density 68/sq mi (26/km²)
Congressional district 12th
Time zone Central: UTC-6/-5

Jefferson County is a county located in the southern part of the U.S. state of Illinois. According to the 2010 census, it has a population of 38,827.[1] The county seat is Mount Vernon.[2]

Jefferson County comprises the Mount Vernon, IL Micropolitan Statistical Area. It is located in the southern portion known locally as "Little Egypt".

The western border of the county adjoins the Greater St. Louis consolidated metropolitan statistical area, the Metro-East region, and the St. Louis commuter region and market and viewing area.


  • History 1
  • Geography 2
    • Climate and weather 2.1
    • Major highways 2.2
    • Adjacent counties 2.3
  • Demographics 3
  • Agencies 4
  • Communities 5
    • Cities 5.1
    • Villages 5.2
    • Unincorporated communities 5.3
    • Townships 5.4
  • See also 6
  • References 7


The first settler in Jefferson County is believed to have been Andrew Moore. In 1810, he settled near the southeast corner of the county, near where the Goshen Road emerges from the forest of Hamilton County into what is now known as Moore's Prairie. It is interesting that Moore arrived from the Goshen Settlement, near Edwardsville. His migration was therefore retrograde, from the west toward the interior of the State.

In 1814, Andrew Moore departed with his eight-year-old son for Jordan's settlement, a journey from which he never returned. A skull that was believed to have been Moore's was found several years later about two miles from his cabin. Jordan's Settlement, also called Jordan's Fort, was southeast of modern Thompsonville, Illinois, about twenty miles south of Moore's cabin. This episode occurred during the War of 1812 when many of the Indian tribes were allied with the British.

In 1816, Carter Wilkey, Daniel Crenshaw and Robert Cook settled in Moore's Prairie. Daniel Crenshaw moved into Moore's cabin. This settlement is believed to be the first permanent settlement in the County.

Jefferson County was organized in 1819, out of parts of White, Edwards and Franklin Counties. It was named in honor of Thomas Jefferson, principle draftsman of the Northwest Ordinance, among other things.[3] The baseline along the northern border of the County crosses the Third Principal Meridian at the northwest corner of the County.


According to the U.S. Census Bureau, the county has a total area of 584 square miles (1,510 km2), of which 571 square miles (1,480 km2) is land and 13 square miles (34 km2) (2.2%) is water.[4]

Climate and weather

Mount Vernon, Illinois
Climate chart ()
Average max. and min. temperatures in °F
Precipitation totals in inches
Source: The Weather Channel[5]

In recent years, average temperatures in the county seat of Mount Vernon have ranged from a low of 19 °F (−7 °C) in January to a high of 88 °F (31 °C) in July, although a record low of −21 °F (−29 °C) was recorded in January 1994 and a record high of 114 °F (46 °C) was recorded in July 1936. Average monthly precipitation ranged from 2.45 inches (62 mm) in January to 4.58 inches (116 mm) in May.[5]

Major highways

Adjacent counties


2000 census age pyramid for Jefferson County

As of the 2010 United States Census, there were 38,827 people, 15,365 households, and 10,140 families residing in the county.[11] The population density was 68.0 inhabitants per square mile (26.3/km2). There were 16,954 housing units at an average density of 29.7 per square mile (11.5/km2).[4] The racial makeup of the county was 88.4% white, 8.4% black or African American, 0.6% Asian, 0.2% American Indian, 0.8% from other races, and 1.6% from two or more races. Those of Hispanic or Latino origin made up 2.1% of the population.[11] In terms of ancestry, 24.3% were German, 15.8% were Irish, 13.6% were English, and 10.2% were American.[12]

Of the 15,365 households, 30.1% had children under the age of 18 living with them, 50.0% were married couples living together, 11.4% had a female householder with no husband present, 34.0% were non-families, and 29.1% of all households were made up of individuals. The average household size was 2.38 and the average family size was 2.92. The median age was 40.6 years.[11]

The median income for a household in the county was $41,161 and the median income for a family was $51,262. Males had a median income of $41,193 versus $29,645 for females. The per capita income for the county was $21,370. About 12.4% of families and 17.1% of the population were below the poverty line, including 24.8% of those under age 18 and 10.7% of those age 65 or over.[13]


In 2015 the county police department announced that the words "In God We Trust" will be on police squad cars.[14]




Unincorporated communities


Jefferson County is divided into sixteen townships:

See also


  1. ^ a b "State & County QuickFacts". United States Census Bureau. Retrieved July 6, 2014. 
  2. ^ "Find a County". National Association of Counties. Retrieved 2011-06-07. 
  3. ^ Gannett, Henry (1905). The Origin of Certain Place Names in the United States. Govt. Print. Off. p. 168. 
  4. ^ a b "Population, Housing Units, Area, and Density: 2010 - County".  
  5. ^ a b "Monthly Averages for Mount Vernon, Illinois". The Weather Channel. Retrieved 2011-01-27. 
  6. ^ "Annual Estimates of the Resident Population for Incorporated Places: April 1, 2010 to July 1, 2014". Retrieved June 4, 2015. 
  7. ^ "U.S. Decennial Census". United States Census Bureau. Retrieved July 6, 2014. 
  8. ^ "Historical Census Browser". University of Virginia Library. Retrieved July 6, 2014. 
  9. ^ "Population of Counties by Decennial Census: 1900 to 1990". United States Census Bureau. Retrieved July 6, 2014. 
  10. ^ "Census 2000 PHC-T-4. Ranking Tables for Counties: 1990 and 2000" (PDF). United States Census Bureau. Retrieved July 6, 2014. 
  11. ^ a b c "DP-1 Profile of General Population and Housing Characteristics: 2010 Demographic Profile Data".  
  12. ^ "DP02 SELECTED SOCIAL CHARACTERISTICS IN THE UNITED STATES – 2006-2010 American Community Survey 5-Year Estimates".  
  13. ^ "DP03 SELECTED ECONOMIC CHARACTERISTICS – 2006-2010 American Community Survey 5-Year Estimates".  
  14. ^ "'In God We Trust' to be placed on Jefferson Co., IL squad cars" (Archive). KFVS. August 1, 2015. Retrieved on August 2, 2015.

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