Illinois Counties
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Illinois Counties

There are one hundred and two counties in Illinois. St. Clair County was the first county established in what is today Illinois. Most counties in Illinois were named after early American leaders, especially of the American Revolutionary War, as well as soldiers from the Battle of Tippecanoe and the War of 1812.

Warren County, Illinois

Warren County Education, Geography, and HistoryWarren County, Illinois Courthouse

Warren County is a county located in the state of Illinois. According to the 2010 census, it had a population of 17,707. Warren County was created on January 13, 1825. The county seat is Monmouth. The county is named for General Joseph Warren (1741-1775), played a role in American Patriot movements, a prominent early fatality in the American Revolutionary War.      

Etymology - Origin of Warren County Name

The county is named for General Joseph Warren, pioneer physician and revolutionary soldier killed at Bunker Hill.


County QuickFacts: CensusBureau Quick Facts

Warren County History

Warren County was created on January 13, 1825 (Laws, 1825, p. 93) and was formed from unorganized land (Pike County). County organization was completed in July, 1830. Present area, or parts of it, formerly included in: Attached to Peoria County [Laws, 1826, p. 76-77] (1826-1830), Attached to Schuyler County [Laws, 1825, p. 95] (1825-1826), Pike County (1812-1825), Madison County (1812-1821) and St. Clair County (1795-1812).

The County was named for Joseph Warren, a physician and soldier who served at Lexington, a Major General of the Massachusetts militia. He was killed at the battle of Bunker Hill. The County Seat is Monmouth . Prior County Seats was House of Alexis Phelps, at Lower Yellow Banks, now Oquawka- Temporary designation (1830-1831) and Monmouth (1831-Present).

Geography: Land and Water

As reported by the Census Bureau, the county has a total area of 543 square miles (1,407 km2), of which, 543 square miles (1,405 km2) of it is land and 1 square miles (2 km2) of it (0.12%) is water.

Warren county is located in northwest Illinois.

Neighboring Counties

Bordering counties are as follows:

  • Northeast: Knox County
  • Southeast: Fulton County
  • South: McDonough County
  • West: Henderson County
  • Northwest: Mercer County


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