Data / Population / Mercer County

Population in Mercer County

Population in Mercer County was 15,229 in 2025, according to the U.S. Census Bureau. That is down 0.4% from 2024. That is the 68th highest of 102 counties in 2025.

2025, persons15,229
Change on 2024-0.4%
Rank68th of 102Counties in Illinois ranked
Series high15,6372020
Series low15,2292025

Population in Mercer County, 2020 to 2025

CSVChart (SVG)

15.2K15.3K15.4K15.5K15.6K15.7K2020202120222023202420252020: 15,637 persons2021: 15,587 persons2022: 15,511 persons2023: 15,472 persons2024: 15,292 persons2025: 15,229 persons
persons. Source: U.S. Census Bureau. Retrieved 2026-10-08, published 2026-03-26.
All 6 values
Periodpersons
202515,229
202415,292
202315,472
202215,511
202115,587
202015,637

Compared with Illinois and United States

Place2025
Mercer County15,229
Illinois12,719,141
United States341,784,857

Rankings

Definition

Resident population. Spain and the EU: 1 January, with Spanish figures from the official municipal register (Padrón). United States: Census Bureau population estimates for 1 July. Other countries and the World: World Bank mid-year estimates, which count all residents regardless of legal status or citizenship.

For Denmark, Statistics Denmark counts the registered resident population on 1 January. Greenland and the Faroe Islands are excluded. The annual series selects the first-quarter reference date from FOLK1A. The World Bank series exists for every country, so use it (through compare) to rank countries on one basis.

How to cite

U.S. Census Bureau. Annual estimates of the resident population for the United States, states and counties, 1 July (Population Estimates Program). https://www2.census.gov/programs-surveys/popest/datasets/2020-2025/. Retrieved 2026-10-08.

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Questions

What is the population in Mercer County?

Population in Mercer County was 15,229 in 2025, according to the U.S. Census Bureau. That is down 0.4% from 2024. That is the 68th highest of 102 counties in 2025.

Where does this figure come from?

U.S. Census Bureau. Annual estimates of the resident population for the United States, states and counties, 1 July (Population Estimates Program). Retrieved by Invokely on 2026-10-08.

What was the highest population in Mercer County?

15,637 in 2020, the highest value since 2020 in this series.

More statistics for Mercer County

All statistics for Mercer County