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Grundy County, Illinois
Map of Illinois highlighting Grundy County
Location in the state of Illinois
Map of the U.S. highlighting Illinois
Illinois's location in the U.S.
Founded 1841
Seat Morris
Largest city Morris
 - Total
 - Land
 - Water

430 sq mi (1,115 km²)
420 sq mi (1,088 km²)
11 sq mi (27 km²), 2.44%
 - (2000)
 - Density

89/sq mi (35/km²)
Time zone Central: UTC-6/-5

Grundy County is a county located in the U.S. state of Illinois. As of 2000, the population was 37,535. Its county seat is Morris6. The center of population of Illinois is located in Grundy County, in the village of Mazon [1]. This county is part of the Chicago metropolitan area. Illinois' State Fossil, the unique and bizarre Tully Monster was first found in Mazon Creek.


According to the U.S. Census Bureau, the county has a total area of 1,115 km² (430 sq mi). 1,088 km² (420 sq mi) of it is land and 27 km² (11 sq mi) of it (2.44%) is water.

Adjacent Counties[]


Grundy County was formed in 1841 out of LaSalle County. It was named for Felix Grundy, who held many political offices. He was United States Senator for Tennessee and Attorney General of the United States in the years leading up to his death in 1840.


Grundy County
Population by year

2000 - 37,535
1990 - 32,337
1980 - 30,582
1970 - 26,535
1960 - 22,350
1950 - 19,217
1940 - 18,398
1930 - 18,678
1920 - 18,580
1910 - 24,162
1900 - 24,136
1890 - 21,024
1880 - 16,732
1870 - 14,938
1860 - 10,379
1850 - 3,023

2000 census age pyramid for Grundy County.

As of the census² of 2000, there were 37,535 people, 14,293 households, and 10,276 families residing in the county. The population density was 35/km² (89/sq mi). There were 15,040 housing units at an average density of 14/km² (36/sq mi). The racial makeup of the county was 97.09% White, 0.19% Black or African American, 0.24% Native American, 0.30% Asian, 0.01% Pacific Islander, 1.30% from other races, and 0.87% from two or more races. 4.13% of the population were Hispanic or Latino of any race.

There were 14,293 households out of which 35.30% had children under the age of 18 living with them, 59.60% were married couples living together, 8.60% had a female householder with no husband present, and 28.10% were non-families. 23.50% of all households were made up of individuals and 9.40% had someone living alone who was 65 years of age or older. The average household size was 2.60 and the average family size was 3.09.

In the county the population was spread out with 26.60% under the age of 18, 8.30% from 18 to 24, 30.20% from 25 to 44, 22.50% from 45 to 64, and 12.30% who were 65 years of age or older. The median age was 36 years. For every 100 females there were 98.90 males. For every 100 females age 18 and over, there were 97.40 males.

The median income for a home in the county is $51,719, and the median income for a family was $60,862. Males had a median income of $46,392 versus $26,487 for females. The per capita income for the county was $22,591. About 3.20% of families and 4.80% of the population were below the poverty line, including 5.00% of those under age 18 and 6.00% of those age 65 or over.


  • Aux Sable Township
  • Braceville Township
  • Erienna Township
  • Felix Township
  • Garfield Township
  • Goodfarm Township
  • Goose Lake Township
  • Greenfield Township
  • Highland Township
  • Maine Township
  • Mazon Township
  • Morris Township
  • Nettle Creek Township
  • Norman Township
  • Saratoga Township
  • Vienna Township
  • Wauponsee Township

Cities and towns[]


  • Forstall, Richard L. (editor) (1996). Population of states and counties of the United States: 1790 to 1990 : from the twenty-one decennial censuses. United States Department of Commerce, Bureau of the Census, Population Division. ISBN 0-934213-48-8. 

Coordinates: 41°17′N 88°26′W / 41.29, -88.43

This page uses content from the English language Wikipedia. The original content was at Grundy 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.