St. Clair County Demographics

A map of St. Clair County's Population by Race

Race	2024 Pop	2020 Pop	2024 %	2020 %
White	149,879	150,496	59.1%	58.5%
Black	70,203	76,013	27.7%	29.5%
Multiracial	14,840	12,863	5.8%	5.0%
Hispanic	12,858	12,582	5.1%	4.9%
Asian	4,098	3,623	1.6%	1.4%
Native American/Other	1,816	1,823	0.7%	0.7%

St. Clair County, Illinois has an estimated population of 253,694, a slight decrease from the 257,400 recorded in the 2020 Census. The population is 59.1% White, 27.7% Black, 5.8% Multiracial, 5.1% Hispanic, 1.6% Asian, and 0.7% Native American/Other. This demographic dot map shows the population of St. Clair County, with one dot drawn for each person counted by the Census, color-coded by race.

St. Clair is about as racially diverse as it was in the 2020 Census. It is less diverse than Illinois overall. Demographers use a diversity index to measure the probability that two randomly selected individuals belong to different racial or ethnic groups. In St. Clair County, that probability was 56.6% in 2020 and 56.8% in the most recent ACS estimates.

St. Clair County is ranked the 9th most populous county in Illinois, out of 102 counties. St. Clair County was ranked the 9th most populous county in the 2020 Census.

St. Clair County's White Population

149,879 residents of St. Clair County, or 59.1% of the population, identify as White. The share of White residents in St. Clair County is comparable to the share in Illinois overall, where 58.1% of the population is White. St. Clair County ranks 99th statewide in terms of White residents as a share of the population, out of 102 counties.

Since the 2020 Census, St. Clair County's White population has remained roughly the same. White residents' share of St. Clair County's population has increased from 58.5% to 59.1%.

St. Clair County is more White than neighboring St. Louis County (44.4% White). St. Clair County is less White than neighboring Monroe County (95% White), Madison County (81.8% White), Randolph County (85.1% White), and Clinton County (90.1% White).

St. Clair County's Black Population

70,203 residents of St. Clair County, or 27.7% of the population, identify as Black. The share of Black residents in St. Clair County is considerably higher than in Illinois overall, where 13.3% of the population is Black. St. Clair County ranks 2nd statewide in terms of Black residents as a share of the population, out of 102 counties.

Since the 2020 Census, St. Clair County's Black population has declined by an estimated 7.6%. Black residents' share of St. Clair County's population has decreased from 29.5% to 27.7%.

St. Clair County is more Black than neighboring Monroe County (0.6% Black), Madison County (7.7% Black), Randolph County (8.2% Black), and Clinton County (3.1% Black). St. Clair County is less Black than neighboring St. Louis County (42.1% Black).

St. Clair County's Asian Population

4,098 residents of St. Clair County, or 1.6% of the population, identify as Asian. The share of Asian residents in St. Clair County is slightly lower than in Illinois overall, where 5.9% of the population is Asian. St. Clair County ranks 20th statewide in terms of Asian residents as a share of the population, out of 102 counties.

Since the 2020 Census, St. Clair County's Asian population has grown by an estimated 13.1%. Asian residents' share of St. Clair County's population has remained roughly unchanged at 1.6%.

St. Clair County is more Asian than neighboring Monroe County (0.6% Asian), Madison County (0.8% Asian), Randolph County (0.6% Asian), and Clinton County (0.6% Asian). St. Clair County is less Asian than neighboring St. Louis County (3.5% Asian).

St. Clair County's Hispanic Population

12,858 residents of St. Clair County, or 5.1% of the population, identify as Hispanic. The share of Hispanic residents in St. Clair County is considerably lower than in Illinois overall, where 18.8% of the population is Hispanic. St. Clair County ranks 34th statewide in terms of Hispanic residents as a share of the population, out of 102 counties.

Since the 2020 Census, St. Clair County's Hispanic population has grown by an estimated 2.2%. Hispanic residents' share of St. Clair County's population has remained roughly unchanged at 5.1%.

St. Clair County is more Hispanic than neighboring Monroe County (1.9% Hispanic), Madison County (4.3% Hispanic), Randolph County (3.8% Hispanic), and Clinton County (4.1% Hispanic). St. Clair County is less Hispanic than neighboring St. Louis County (5.3% Hispanic).

St. Clair County's Native American/Other Population

1,816 residents of St. Clair County, or 0.7% of the population, identify as American Indian/Alaska Native/Native Hawaiian/Pacific Islander/Other. The share of Native American/Other residents in St. Clair County is comparable to the share in Illinois overall, where 0.5% of the population is Native American/Other. St. Clair County ranks 5th statewide in terms of Native American/Other residents as a share of the population, out of 102 counties.

Since the 2020 Census, St. Clair County's Native American/Other population has remained roughly the same. Native American/Other residents' share of St. Clair County's population has remained roughly unchanged at 0.7%.

St. Clair County is more Native American/Other than neighboring Monroe County (0.2% Native American/Other), St. Louis County (0.6% Native American/Other), Madison County (0.3% Native American/Other), Randolph County (0.4% Native American/Other), and Clinton County (0.2% Native American/Other).

St. Clair County's Multiracial Population

14,840 residents of St. Clair County, or 5.8% of the population, identify as Multiracial. The share of Multiracial residents in St. Clair County is slightly higher than in Illinois overall, where 3.4% of the population is Multiracial. St. Clair County ranks 3rd statewide in terms of Multiracial residents as a share of the population, out of 102 counties.

Since the 2020 Census, St. Clair County's Multiracial population has grown by an estimated 15.4%. Multiracial residents' share of St. Clair County's population has increased from 5.0% to 5.8%.

St. Clair County is more Multiracial than neighboring Monroe County (1.6% Multiracial), St. Louis County (4% Multiracial), Madison County (5% Multiracial), Randolph County (1.9% Multiracial), and Clinton County (2% Multiracial).

Sources: Most recent population estimates are from the 2020-2024 American Community Survey 5-Year Estimates. 2020 population counts and map data are from 2020 Census State Redistricting Data. Geographic data are from Census TIGER/Line Shapefiles.