Algonquin Population

1880–2026

31,039

2026 projection

4.5% since 2020 (increase)

05K10K15K20K25K30K35K18801900192019401960198020002020

Source: U.S. Census Bureau decennial counts and annual estimates, including 2010–2020 intercensal estimates. 2026 is a projection. Values between recorded years are interpolated.

Use the left and right arrow keys to inspect population observations.

Population by year

Population estimates for Algonquin. Annual change is shown as a percentage. Growth is the total change since the preceding observation.
202631,039+2150.70%
202530,824+2960.97%
202430,528+3301.09%
202330,198+2490.83%
202229,949-140.05%
202129,963+2630.89%
202029,700-1830.61%
201929,883-910.30%
201829,974-1450.48%
201730,119-980.32%

Showing 10 of 29 years.

The 2020 row compares the April 1 Census count with the July 1, 2019 estimate (about nine months). Its Growth and Annual change therefore do not represent a full year.

Growth since 2020, compared

Algonquin is growing faster than McHenry County, Illinois, and the U.S.

  • Algonquin+3.9%
  • United States+3.1%
  • McHenry County+2.5%
  • Illinois−0.6%

Change from July 1, 2020 to July 1, 2025 population estimates—not annualized growth or site projections.

Source: U.S. Census Bureau. U.S. totals are summed from the 50 states and D.C.; unavailable comparisons are omitted.

Algonquin Demographics

41.4median age

Median age

Female41.8 yrs
Male41 yrs

Adults

23,815
4,502 seniors (65+) · 19% of adults19,313 other adults

Sex

Female 49.8% · 14,979Male 50.2% · 15,088

Population by age

MaleFemale85+ years, male: 26685+ years, female: 28580–84 years, male: 15580–84 years, female: 30075–79 years, male: 47175–79 years, female: 57370–74 years, male: 41770–74 years, female: 51165–69 years, male: 82165–69 years, female: 70360–64 years, male: 1,34260–64 years, female: 1,28155–59 years, male: 1,44455–59 years, female: 1,38950–54 years, male: 85150–54 years, female: 1,07145–49 years, male: 1,13345–49 years, female: 86440–44 years, male: 84140–44 years, female: 79235–39 years, male: 95035–39 years, female: 95430–34 years, male: 1,07630–34 years, female: 1,12525–29 years, male: 84925–29 years, female: 76120–24 years, male: 1,20220–24 years, female: 72115–19 years, male: 1,10815–19 years, female: 71010–14 years, male: 56710–14 years, female: 1,0585–9 years, male: 8675–9 years, female: 8980–4 years, male: 7280–4 years, female: 98385+80–8475–7970–7465–6960–6455–5950–5445–4940–4435–3930–3425–2920–2415–1910–145–90–45005001K1K

Hover or tap an age group to see exact counts. Use the up and down arrow keys to inspect age groups.

U.S. Census Bureau, 2024 ACS 5-year estimates · Table S0101

Race and ethnicity

Tap a square or a group below to highlight it.

Each square is about 1% of residents (roughly 301 people).

Hispanic or Latino residents can be of any race. All other groups exclude Hispanic residents.

U.S. Census Bureau, 2024 ACS 5-year estimates · Table B03002

Algonquin Income

$134,525median household income

Median household income

$134,525

Half of households earn more, half earn less

Median earnings

$72,314

Typical yearly pay for a worker 25 or older.

Poverty rate

4.1%

About 1 in 24 residents

U.S. Census Bureau, 2024 ACS 5-year estimates · Tables S1901, S1501, S1701

Algonquin Marital Status

60% of residents age 15 and older are married.

MarriedNever married
Overall
Male
Female
Marital status of residents age 15 and older
StatusOverallMaleFemale
Married60%59%61%
Never married27%31%22%
Divorced9%7%10%
Widowed4%2%7%
Separated<1%1%<1%

U.S. Census Bureau, 2024 ACS 5-year estimates · Table S1201

Sources

14 sources

Population

American Community Survey, 2024 5-year

Additional sources