Richest Counties in Illinois (2024)

by Kristen Carney Kristen Carney

Updated: June 20, 2024

Richest County in Illinois

The richest county in Illinois is Lake County with an average household income of $147,075 as of 2022 and 708,760 people as of 2023 according to the most current Census data available (citation).

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20 Richest Counties in Illinois

Rank County Population Average Income Median Income
1 Lake County 708,760 $147,075 $104,553
2 DuPage County 921,213 $144,731 $107,035
3 Will County 700,728 $126,188 $103,678
4 Kane County 514,982 $125,010 $96,400
5 McHenry County 312,800 $123,694 $100,101
6 Kendall County 139,976 $121,223 $106,358
7 Monroe County 34,957 $119,329 $100,685
8 Cook County 5,087,072 $113,411 $78,304
9 Grundy County 53,578 $107,987 $89,993
10 Calhoun County 4,317 $106,062 $88,059
11 Woodford County 38,285 $103,919 $80,093
12 Boone County 53,202 $100,719 $80,502
13 Piatt County 16,714 $100,385 $81,151
14 Clinton County 36,785 $99,933 $78,054
15 McLean County 170,441 $99,327 $75,356
16 Menard County 11,954 $99,217 $84,846
17 Jersey County 21,091 $97,649 $77,607
18 Sangamon County 193,491 $94,790 $71,653
19 Madison County 262,752 $93,528 $71,759
20 Effingham County 34,331 $93,523 $73,181

Median Income versus Average Income: Which Should You Use?

We usually suggest using median income data – either instead of or in addition to – average income data as a true indicator of wealth. If you haven’t thought about median versus average since your last standardized test, you aren’t alone. Here’s what they are:

  • average is the sum of a set of numbers divided by the count of numbers in the set
  • median is the middle number in the set of numbers
illustation of median vs average

Now let’s say you had the following simplified set of income data.

Household 1: $30,000
Household 2: $50,000
Household 3: $1,000,000

The average income for this set is $360,000. The outlier data point ($1,000,000) skews the average WAY up. Conversely, the average income would be skewed WAY down if someone had an income of $500. The median income for the same data set is $50,000. Outlier data doesn’t skew the median.

Most Business Owners Should Use Median Income

So most business owners should use the median income as a true indicator of wealth, because it provides a more accurate representation of a typical income, especially in areas with significant income disparity.

When Should You Use Average Income

If your target market is high-income households, the average income may be more relevant. This is because the average income can highlight the presence of a higher concentration of wealthy individuals, which is beneficial for luxury goods and services marketing. We’re using average income on this page because using the Census’s highest reported median value of $250,001 could result in multiple ties for the richest geography.

Why do so many cities have a median value of $250,001?

The Census' American Community Survey uses $250,000+ as a jam value for median income estimates to protect privacy, ensure data consistency, and simplify reporting. A "jam value" in survey data refers to a placeholder or default value used when actual data points are unavailable, incomplete, or exceed certain thresholds. We represent this jam value as $250,001 to make it easy for you to sort.

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SOURCES

United States Census Bureau. Annual Estimates of the Resident Population: April 1, 2020 to July 1, 2023. U.S. Census Bureau, Population Division. Web. May 2024. http://www.census.gov/.

United States Census Bureau. B01001 SEX BY AGE, 2022 American Community Survey 5-Year Estimates. U.S. Census Bureau, American Community Survey Office. Web. 7 December 2023. http://www.census.gov/.

United States Census Bureau. B19013 Median Household Income, 2022 American Community Survey 5-Year Estimates. U.S. Census Bureau, American Community Survey Office. Web. 7 December 2023. http://www.census.gov/.

United States Census Bureau. “DP03 SELECTED ECONOMIC CHARACTERISTICS.” 2022 American Community Survey 5-Year Estimates. U.S. Census Bureau, American Community Survey Office. Web. 07 December 2023. http://www.census.gov/.

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