- Lead
- 25,206
- Total
- 113,653
- vs nation
- D+23.6
Illinois 21st State Senate District
President margin by year
Place winner margin
President results by year
Modeled candidate-vote estimate on current district boundaries
- Lead
- 30,473
- Total
- 121,634
- vs nation
- D+20.6
- Lead
- 20,279
- Total
- 108,292
- vs nation
- D+16.6
- Lead
- 8,083
- Total
- 98,957
- vs nation
- D+4.3
- Lead
- 18,039
- Total
- 103,792
- vs nation
- D+10.1
- Lead
- 2,587
- Total
- 96,994
- vs nation
- R+0.2
- Lead
- 5,005
- Total
- 85,369
- vs nation
- R+6.4
- Lead
- 2,571
- Total
- 75,831
- vs nation
- R+11.9
Key facts
- 2024 presidential margin
- D+22.2MIT Election Lab
- Population
- 217,2562024 5-year
- Population density
- 3,482 / sq mi2024 5-year · TIGER/Line
- Land area
- 62.4 sq miTIGER/Line
- Median household income
- $125,6452024 5-year
- White (non-Hispanic)
- 68.1%2024 5-year
- Black
- 4.9%2024 5-year
- Hispanic / Latino
- 9.0%2024 5-year
- Peak Democratic margin
- D+25.1 in 2020MIT Election Lab
- Peak Republican margin
- R+56.5 in 1920MIT Election Lab
- Most similar
- State Senate District 41, IL · twin score 93.6
presidential history
Party record book
Illinois 21st State Senate District · the strongest Democratic and Republican presidential performances recorded here, measured three ways.
1892–2024 (partial returns from 1876) · 38 presidential cycles · 38 with a vote-share denominator · 34 with a national benchmark
Highest vote share
Largest share of the presidential candidate vote cast here.
Democratic
Joe Biden2020
61.2%
74,392 votes · D+25.1 · modeled estimate
Runner-up · Kamala Harris, 2024 · 59.4%
Republican
Dwight D. Eisenhower1956
75.4%
20,269 votes · R+50.8 · modeled estimate
Runner-up · Warren G. Harding, 1920 · 75.1%
Most votes
Largest number of votes cast for the party’s presidential nominee here.
Democratic
Joe Biden2020
74,392votes
61.2% of the vote · D+25.1 · modeled estimate
Runner-up · Kamala Harris, 2024 · 67,510 votes
Republican
George W. Bush2004
49,249votes
50.8% of the vote · R+2.7 · modeled estimate
Runner-up · Ronald Reagan, 1984 · 48,199 votes
Best relative to the U.S.
This Place’s margin against the national margin in the same election — positive when it leaned toward the party more than the country did.
Democratic
Kamala Harris2024
+23.6pts D vs U.S.
Place D+22.2 · U.S. R+1.5 · modeled estimate
Runner-up · Joe Biden, 2020 · +20.6 pts
Republican
Thomas E. Dewey1948
+38.2pts R vs U.S.
Place R+33.7 · U.S. D+4.5 · modeled estimate
Runner-up · Dwight D. Eisenhower, 1956 · +35.4 pts
Current officeholders
State legislative officeholder from OpenStates nightly current-legislator data.
Senate and governor results are in the Office selector at the top of this page.
U.S. House
Each row is a county-allocated estimate of U.S. House votes for this district — county returns apportioned onto its boundary, not precinct-counted. “Vote lead” is the estimated local lead here, not necessarily the winner of the full contest.
| Year | Vote lead | Democratic | Republican | Total |
|---|---|---|---|---|
| 2024 | D | 55.7%58,042 | 44.3%46,249 | 104,291 |
| 2020 | D | 62.6%62,953 | 37.4%37,686 | 100,639 |
Illinois 21st State Senate District sits in the Upper Midwest. In 2024 it voted Democratic.
Across the recorded series it reached a Democratic high of 25.1 points in 2020 and a Republican high of 56.5 points in 1920. Between 2020 and 2024 the district moved 2.9 points toward the Republican candidate; the 2024 margin was 22.2 points.
A population of 217,256, a 68% non-Hispanic-white share, and a median household income of $125,645 describe the district. The district's voting pattern over the last decade is most similar to that of State Senate District 41 and State Senate District 27.
The state-senate districts whose fingerprint — 2000–2024 trajectory, demographics, ancestry, religion — sits closest to this one, and why.
Twin score (0–100) = weighted cosine between tier-standardized fingerprints: presidential margins 2000–2024 with 12-yr trend and elasticity, ACS income, age, education, population and race, top reported ancestries, and religious adherence — chips name the closest-shared dimensions and the widest gap. Re-weight the groups in the twins explorer.
District research tools
Open the source-auditable district brief for electoral baseline, electorate, current-cycle coverage, geography, official dates, and methodology. Open campaign intelligence report → · Browse all comparisons →
Illinois 21st State Senate District. Akashic. https://akashic.app/sld-upper/17021/. Accessed May 20, 2026. License: CC BY 4.0.