Johnson County, Illinois Demographics 2026

Population Overview

Johnson County is located in Illinois with a total population of 13,376. It is the 79th most populous county out of 102 in Illinois. The county encompasses 7 Census-designated places.

Age Demographics

The median age in Johnson County is 41.4 years. This is 6% higher than the state median of 39.0 years.

Economy, Income & Housing

The median household income in Johnson County is $62,528. This is 25% lower than the state median of $83,390. It is also 23% lower than the national median of $80,734. The poverty rate stands at 17.6%. This is 49% higher than the state poverty rate of 11.8%. The unemployment rate is 3.5%. This is 40% lower than the state rate of 5.8%. The median home value is $160,500. Housing costs are 39% lower than the state median of $263,300. With a home-value-to-income ratio of just 2.6x, Johnson County is one of the most affordable housing markets in the area. 82.0% of occupied housing units are owner-occupied. This homeownership rate is 22% higher than the state average of 67.1%.

Race & Ethnicity

The largest racial or ethnic group in Johnson County is White (non-Hispanic), making up 80.1% of the population. Black or African American residents account for 7.8%. The Hispanic or Latino population (4.5%) is well below the state average of 18.8%. The Asian population (0.3%) is well below the state average of 5.9%.

Education

19.6% of residents aged 25 and older hold a bachelor's degree or higher. This is 48% lower than the state rate of 37.9%. Nationally, 35.7% of adults hold at least a bachelor's degree. The high school graduation rate (or equivalent) is 85.4%.

Data Sources & Methodology

All figures for Johnson County come from the U.S. Census Bureau's American Community Survey (ACS) 2020–2024 5-Year Estimates, with comparisons drawn against Illinois and national averages from the same dataset. See our methodology page for how each metric is defined, or data.census.gov for official tables with margins of error.