Millbrook, Illinois Demographics & Population 2026

A note before these figures: with a population of 243, Millbrook'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

Millbrook is a small community located in Illinois, within Kendall County. The total population is 243. It ranks as the 1148th most populous out of 1,445 Census-designated places in Illinois.

Age Demographics

The median age in Millbrook is 55.3 years. This is 42% higher than the state median of 39.0 years.

Economy, Income & Housing

The median household income in Millbrook is $137,560. This is 65% higher than the state median of $83,390. It is also 70% higher than the national median of $80,734. The poverty rate stands at 4.5%. This is 62% lower than the state poverty rate of 11.8%. This exceptionally low poverty rate indicates strong economic prosperity across the community. The unemployment rate is 2.3%. This is 60% lower than the state rate of 5.8%. The median home value is $361,900. Housing costs are 37% higher than the state median of $263,300. With a home-value-to-income ratio of just 2.6x, Millbrook is one of the most affordable housing markets in the area. 99.0% of occupied housing units are owner-occupied. This homeownership rate is 48% higher than the state average of 67.1%.

Race & Ethnicity

Millbrook has a predominantly White (non-Hispanic) population, comprising 93.4% of all residents. Hispanic or Latino residents account for 1.7%. The White (non-Hispanic) population is significantly higher than the state average (93.4% vs 58.1%). The Hispanic or Latino population (1.7%) is well below the state average of 18.8%.

Education

39.4% of residents aged 25 and older hold a bachelor's degree or higher. This is 4% higher 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 96.0%. Notably, 16.0% of adults hold a graduate or professional degree, indicating a highly educated workforce.

Data Sources & Methodology

All demographic data for Millbrook, 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.