Thayer, Illinois Demographics & Population 2026

A note before these figures: with a population of 531, Thayer'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

Thayer is a small community located in Illinois, within Sangamon County. The total population is 531. It ranks as the 915th most populous out of 1,445 Census-designated places in Illinois.

Age Demographics

The median age in Thayer is 46.4 years. This is 19% higher than the state median of 39.0 years. 11.3% 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 Thayer is $62,083. This is 26% 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 10.5%. This is 11% lower than the state poverty rate of 11.8%. The unemployment rate is 4.4%. This is 24% lower than the state rate of 5.8%. The median home value is $97,100. Housing costs are 63% lower than the state median of $263,300. With a home-value-to-income ratio of just 1.6x, Thayer is one of the most affordable housing markets in the area. 86.9% of occupied housing units are owner-occupied. This homeownership rate is 30% higher than the state average of 67.1%.

Race & Ethnicity

Thayer has a predominantly White (non-Hispanic) population, comprising 95.5% of all residents. Black or African American residents account for 1.3%. The White (non-Hispanic) population is significantly higher than the state average (95.5% vs 58.1%). The Black or African American population (1.3%) is well below the state average of 13.3%. The Asian population (1.1%) is well below the state average of 5.9%.

Education

10.3% of residents aged 25 and older hold a bachelor's degree or higher. This is 73% 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 91.0%.

Data Sources & Methodology

All demographic data for Thayer, 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.