Lake Petersburg, Illinois Demographics & Population 2026

A note before these figures: with a population of 928, Lake Petersburg'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

Lake Petersburg is a small community located in Illinois, within Menard County. The total population is 928. It ranks as the 720th most populous out of 1,445 Census-designated places in Illinois.

Age Demographics

The median age in Lake Petersburg is 60.8 years. This is 56% higher than the state median of 39.0 years. Only 9.8% of residents are under 18, indicating fewer families with children.

Economy, Income & Housing

The median household income in Lake Petersburg is $144,375. This is 73% higher than the state median of $83,390. It is also 79% higher than the national median of $80,734. The poverty rate stands at 2.7%. This is 77% lower than the state poverty rate of 11.8%. This exceptionally low poverty rate indicates strong economic prosperity across the community. The survey records no unemployed residents in Lake Petersburg, which reflects the size of the sample rather than a labor market without joblessness. The median home value is $338,700. Housing costs are 29% higher than the state median of $263,300. With a home-value-to-income ratio of just 2.3x, Lake Petersburg is one of the most affordable housing markets in the area. 97.1% of occupied housing units are owner-occupied. This homeownership rate is 45% higher than the state average of 67.1%.

Race & Ethnicity

Every resident counted in Lake Petersburg was recorded as White (non-Hispanic). A figure of exactly 100.0% reflects a survey sample too small to capture the community's full composition rather than a precise measurement.

Education

48.2% of residents aged 25 and older hold a bachelor's degree or higher. This places Lake Petersburg in the top 10% of all cities in the state for educational attainment. This is 27% higher than the state rate of 37.9%. Nationally, 35.7% of adults hold at least a bachelor's degree. No surveyed resident aged 25 or older reported leaving school before earning a high school diploma, though a rate of exactly 100% reflects the limits of a small sample.

Data Sources & Methodology

All demographic data for Lake Petersburg, 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.