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Monroe County, Illinois
Map of Illinois highlighting Monroe County
Location in the state of Illinois
Map of the U.S. highlighting Illinois
Illinois's location in the U.S.
Founded 1816
Seat Waterloo
Largest city Columbia
 - Total
 - Land
 - Water

398 sq mi (1,030 km²)
388 sq mi (1,006 km²)
9 sq mi (24 km²), 2.37%
 - (2005)
 - Density

71/sq mi (27/km²)
Time zone Central: UTC-6/-5

Monroe County is a county located in the U.S. state of Illinois. Monroe County is part of the St. Louis Metro Area. As of 2000, the population was 27,619. Its county seat is Waterloo6. Its largest city is Columbia.


According to the U.S. Census Bureau, the county has a total area of 1,030 km² (398 sq mi). 1,006 km² (388 sq mi) of it is land and 24 km² (9 sq mi) of it (2.37%) is water.

The western part of the county on the Mississippi River is part of the American Bottom floodplain, while the eastern portion of the county is relatively flat and was originally prairie. The transition zone between has high bluffs of limestone and dolomite and has distinctive Karst topography with numerous sinkholes, caves, and springs.

Adjacent Counties[]


Monroe County was formed in 1816 out of Randolph and St. Clair Counties. It was named in honor of James Monroe, who had just served as United States Secretary of War and who was elected President later that same year. It's original county seat was Harrisonville (Located to the west of the present village of Valmeyer ) until 1825.[1]


Historical populations
Census Pop.
1900 13,847
1910 13,508 −2.4%
1920 12,839 −5.0%
1930 12,369 −3.7%
1940 12,754 3.1%
1950 13,282 4.1%
1960 15,507 16.8%
1970 18,831 21.4%
1980 20,117 6.8%
1990 22,422 11.5%
2000 27,619 23.2%
IL Counties 1900-1990

As of the census² of 2000, there were 27,619 people, 10,275 households, and 7,778 families residing in the county. The population density was 27/km² (71/sq mi). There were 10,749 housing units at an average density of 11/km² (28/sq mi). The racial makeup of the county was 98.77% White, 0.05% Black or African American, 0.19% Native American, 0.31% Asian, 0.18% from other races, and 0.50% from two or more races. 0.74% of the population were Hispanic or Latino of any race.

There were 10,275 households out of which 37.70% had children under the age of 18 living with them, 65.30% were married couples living together, 7.30% had a female householder with no husband present, and 24.30% were non-families. 21.30% of all households were made up of individuals and 9.60% had someone living alone who was 65 years of age or older. The average household size was 2.65 and the average family size was 3.09.

In the county the population was spread out with 26.40% under the age of 18, 7.40% from 18 to 24, 30.60% from 25 to 44, 22.20% from 45 to 64, and 13.40% who were 65 years of age or older. The median age was 38 years. For every 100 females there were 96.80 males. For every 100 females age 18 and over, there were 93.60 males.

The median income for a household in the county was $55,320, and the median income for a family was $62,397. Males had a median income of $41,243 versus $27,130 for females. The per capita income for the county was $22,954. About 2.30% of families and 3.40% of the population were below the poverty line, including 2.80% of those under age 18 and 7.30% of those age 65 or over.

Cities and towns[]

Unincorporated Communities[]

See also[]

Illinois Caverns State Natural Area

External links[]

Coordinates: 38°17′N 90°11′W / 38.28, -90.18

This page uses content from the English language Wikipedia. The original content was at Monroe County, Illinois. The list of authors can be seen in the page history. As with this Familypedia wiki, the content of Wikipedia is available under the Creative Commons License.