Old Mill Creek, Illinois Demographics & Population 2026

A note before these figures: with a population of 143, Old Mill Creek'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

Old Mill Creek is a small community located in Illinois, within Lake County. The total population is 143. It ranks as the 1280th most populous out of 1,445 Census-designated places in Illinois.

Age Demographics

The median age in Old Mill Creek is 47.3 years. This is 21% higher than the state median of 39.0 years. 10.5% 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 Old Mill Creek is $108,333. This is 30% higher than the state median of $83,390. It is also 34% higher than the national median of $80,734. The poverty rate stands at 4.9%. This is 59% 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 6.3%. This is 9% higher than the state rate of 5.8%. The median home value is $450,000. Housing costs are 71% higher than the state median of $263,300. The home-value-to-income ratio is 4.2x. 43.8% of occupied housing units are owner-occupied. This homeownership rate is 35% lower than the state average of 67.1%.

Race & Ethnicity

The largest racial or ethnic group in Old Mill Creek is White (non-Hispanic), making up 82.5% of the population. Hispanic or Latino residents account for 10.5%.

Education

74.3% of residents aged 25 and older hold a bachelor's degree or higher. This places Old Mill Creek in the top 10% of all cities in the state for educational attainment. This is 96% 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 97.1%. Notably, 33.3% of adults hold a graduate or professional degree, indicating a highly educated workforce.

Data Sources & Methodology

All demographic data for Old Mill Creek, 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.