Williamson, Illinois Demographics & Population 2026

A note before these figures: with a population of 160, Williamson's ACS estimates come from a small number of survey responses and carry wide margins of error. Individual percentages below — particularly rates that round to 0% or 100% — are approximations, not precise measurements. See data.census.gov for the published margins of error.

Population Overview

Williamson is a small community located in Illinois, within Madison County. The total population is 160. It ranks as the 1255th most populous out of 1,445 Census-designated places in Illinois.

Age Demographics

The median age in Williamson is 51.0 years. This is 31% higher than the state median of 39.0 years. Only 13.8% of residents are under 18, indicating fewer families with children. 13.8% of residents are 75 or older, suggesting a significant retirement-age population with implications for healthcare services and senior housing.

Economy, Income & Housing

The median household income in Williamson is $57,841. This is 31% lower than the state median of $83,390. It is also 28% lower than the national median of $80,734. The poverty rate stands at 19.6%. This is 66% higher than the state poverty rate of 11.8%. The survey records no unemployed residents in Williamson, which reflects the size of the sample rather than a labor market without joblessness. The median home value is $75,800. Housing costs are 71% lower than the state median of $263,300. With a home-value-to-income ratio of just 1.3x, Williamson is one of the most affordable housing markets in the area. 67.9% of occupied housing units are owner-occupied. This homeownership rate is 1% higher than the state average of 67.1%.

Race & Ethnicity

Williamson has a predominantly White (non-Hispanic) population, comprising 89.4% of all residents. Hispanic or Latino residents account for 5.0%. The White (non-Hispanic) population is significantly higher than the state average (89.4% vs 58.1%). The Hispanic or Latino population (5.0%) is well below the state average of 18.8%.

Education

5.7% of residents aged 25 and older hold a bachelor's degree or higher. This is 85% 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 75.8%.

Data Sources & Methodology

All demographic data for Williamson, Illinois is sourced from the U.S. Census Bureau's American Community Survey (ACS) 2020–2024 5-Year Estimates. The ACS collects data from approximately 3.5 million households annually and pools five years of responses so that even small communities can be measured, though the margin of error widens as the population falls. Comparisons are made against Illinois state averages and national averages calculated from the same dataset. Rankings reflect the city's position among all 1,445 Census-designated places in Illinois. Read more about how these figures are produced on our methodology page, or visit data.census.gov for official data.