Seneca, IL

Village in IL, US

By Neilsberg Research

Last updated May 1, 2026

Key Indicators

A quick look at key numbers

Population

2,450

Source: U.S. Census Bureau American Community Survey (ACS) 2020-2024 5-Year Estimates

Median Age

35.5

years ∙ half population younger than 35.5, half older

Diversity Index

23.9%

chance two random people differ in race and ethnicity

Nativity

foreign-born population

98%Native

2% Foreign-born

Geographic Context

Location, size, and surroundings

About

Seneca is a village within Grundy and LaSalle counties, Illinois, United States.

Location

Village in IL, US

Co-ordinates

DEC41.302634° N, 88.614667° W

DMS41° 18′ 09.48″ N, 88° 36′ 52.80″ W

Population Density & area

395.2/sq mi (152.5/km²)

Total Area

6.57 sq mi (17.02 km²)

Land Area

6.2 sq mi (16.07 km²) · 94.4%

Water Area

0.37 sq mi (0.95 km²) · 5.6%

Demographics & Living

Who lives here, how households are formed, and community composition

Population Composition

Key characteristics of the population

Sex Distribution

54.1% male

Male 54.1%

Female 45.9%

males per 100 females

Seneca 117.8

Illinois 97.7

United States 98

Nativity

foreign-born population

98%Native

2% Foreign-born

% Foreign-born

Seneca 2%

Illinois 14.7%

United States 14.1%

Age Distribution

How the population is spread across age groups

Median Age

35.5

years ∙ half population younger than 35.5, half older

Seneca

35.5

Illinois

United States

38.9

Dependency ratio

68.6

dependents per 100 working-age adults

Seneca 68.6

Illinois 63.5

United States 64.4

AGE DISTRIBUTION

Distribution of age group

Median age

	Seneca	Illinois	United States
Age Group
Children (Under 18)	28.6%	21.8%	22%
Working age (18-64)	59.3%	61.2%	60.8%
Senior (65+)	12.1%	17%	17.2%
Dependency ratio
Total dependency ratio	68.6	63.5	64.4
Child dependency ratio	48.2	35.7	36.1
Old-age dependency ratio	20.4	27.8	28.3

Racial & Ethnic Composition

Racial and ethnic makeup and how it compares

Race & Ethnicity

White

86.6%

Black

0.9%

Asian

Hispanic

10%

Other

2.5%

Note: White, Black, and Asian refer to individuals belonging to a single race and not of Hispanic origin. Hispanics may be of any race.

Diversity Index

23.9%

chance two random people differ in race and ethnicity

Seneca 23.9%

Illinois 60.5%

United States 61.4%

Note: The Diversity Index (DI), based on the Blau Index, measures the probability that two randomly selected individuals differ in race and ethnicity. Values range from 0 (no diversity) to 1 (high diversity) and are shown as percentages.

RACIAL & ETHNIC COMPOSITION

Race & Ethnicity

Percentage of Seneca population

	Seneca	Illinois	United States
Hispanic or Latino	10%	18.8%	19.3%
Mexican	6.1%	14.4%	11.3%
Puerto Rican	0%	1.6%	1.8%
Cuban	0%	0.3%	0.8%
Other Hispanic / Latino	4%	2.5%	5.5%
Not Hispanic or Latino	90%	81.2%	80.7%
One race	87.6%	77.8%	76.4%
White	86.6%	58.1%	57.4%
Black or African American	0.9%	13.3%	11.9%
American Indian and Alaska Native	0%	0.1%	0.5%
Asian	0%	5.9%	5.9%
Native Hawaiian and Other Pacific Islander	0%	0%	0.2%
Some Other Race	0%	0.4%	0.6%
Two or more races (Multiracial)	2.4%	3.4%	4.3%

Household & Families Composition

Household size, type, and family structure

Household structure

70.9% family

Family 70.9%

Non family 29.1%

% family households

Seneca 70.9%

Illinois 62.2%

United States 64.2%

Average household size

2.7

persons per household

Seneca

2.7

Illinois

2.46

United States

2.53

Household & Family COMPOSITION

Households

Percentage of Seneca population

	Seneca	Illinois	United States
Total households	907	5,036,449	129,227,496
Average houshold size	2.7	2.46	2.53
Family households	643	3,130,978	82,990,528
Average family size	3.16	3.14	3.14
Married couple family	460	2,282,435	60,637,388
Other families	183	848,543	22,353,140
Male householder	87	248,521	6,572,819
Female householder	96	600,022	15,780,321
Non-family households	264	1,905,471	46,236,968
One-person households	189	1,569,881	37,140,836
Male householder	106	712,191	16,871,444
Senior (65+) living alone	8	210,051	5,225,110
Female householder	83	857,690	20,269,392
Senior (65+) living alone	45	417,870	10,089,070
Other living arrangements	75	335,590	9,096,132

Housing Profile

Housing stock, ownership, rentals, and cost burdens

Total housing units

968

housing units

Seneca 968

Illinois 5,457,452

United States 143,775,355

Occupancy status

93.7% occupied

Occupied 93.7%

Vacant 6.3%

vacancy rate

Seneca 6.3%

Illinois 7.7%

United States 10.1%

Housing Characteristics

How the housing supply is structured and used

Types of Housing unit

83.8%

Single family houses

83.8%

Apartments in multi-unit structures

9.6%

Mobile homes

6.6%

Boat, RV, van, etc

Median Year Built

1976

Half of houses were built before 1976, and half after.

Historic ∙ 1939 or earlier

12.7%

Postwar & mid-century ∙ 1940 - 1969

26.9%

Late 20th century ∙ 1970 - 1999

34.9%

Modern ∙ 2000 or later

25.5%

Note: Median year built reflects occupied units only; distribution includes all units.

Housing Characteristics

Units, rooms & bedrooms

Physical characteristics of housing units

	Seneca	Illinois	United States
Rooms per unit
Median rooms	5.9	5.6	5.5
1–3 rooms	7%	14.6%	15.1%
4–6 rooms	52.4%	50.9%	51.6%
7+ rooms	40.6%	34.6%	33.4%
Bedrooms
No bedroom / studio	0%	3.1%	2.9%
1 bedroom	4%	11.5%	10.9%
2 bedrooms	22.9%	27.7%	25%
3 bedrooms	44.7%	35.8%	38.7%
4+ bedrooms	28.3%	21.7%	22.4%
At a glance
Median year built	1976	1971	1981
Total housing units	968	5,457,452	143,775,355

Occupancy Profile

Who is inside and how they use it

Homeownership

81.3% owners

Renter-occupied 18.7%

Owner-occupied 81.3%

homeownership rate

Seneca 81.3%

Illinois 67.1%

United States 65.2%

Average household size

2.64

Owner-occupied

2.98

Renter-occupied

owner-occupied average size

Seneca 2.64

Illinois 2.62

United States 2.64

Housing Characteristics

Occupied unit characteristics

Tenure, crowding, and utilities

	Seneca	Illinois	United States
Total occupied units	907	5,036,449	129,227,496
Year moved in
2020 or later	10%	23.3%	24.8%
2010 to 2019	40.1%	38.1%	39.6%
2000 to 2009	19.4%	17.3%	16.4%
1999 or earlier	30.4%	21.3%	19.1%
Occupants per room
1.00 or fewer	95.3%	97.5%	96.6%
1.01 to 1.50	2.1%	1.6%	2.2%
1.51 or more	2.6%	0.8%	1.2%
Vehicles availability
No vehicles	1.7%	11%	8.4%
1 vehicle	21.4%	35.7%	33.1%
2 vehicles	48.3%	35.1%	36.6%
3 or more vehicles	28.7%	18.3%	21.9%
House heating fuel used
Gas	91.9%	79.5%	51.4%
Electricity	8.2%	18.6%	41.3%
Solar	0%	0.1%	0.3%
Fuel oil, kerosene etc	0%	0.1%	3.9%
All other fuels	0%	0.8%	2%
No fuel used	0%	0.8%	1.2%
Selected characteristics
Lacking complete plumbing	0%	0.3%	0.4%
Lacking complete kitchen	0%	0.8%	0.8%
No telephone service available	0%	0.8%	0.9%

Housing Value

What owner-occupied units are worth

Median home value

$227,500

owner-occupied units

Median value(USD)

Seneca

$227,500

Illinois

$263,300

United States

$332,700

Housing Cost Burden

23.7%

of homeowners with a mortgage are cost-burdened

% Cost-Burdened Households

Owners with a mortgage

23.7%

Owners without a mortgage

4.5%

Renters

18.5%

Note: Households spending 30% or more of their income on housing costs are considered cost-burdened.

Financial characteristics

Property value and housing costs

Tenure, crowding, and utilities

	Seneca	Illinois	United States
Property value
Median Value	$227,500	$263,300	$332,700
Under $100,000	10.1%	13.7%	11.4%
$100,000 - $200,000	31.6%	21.5%	15.8%
$200,000 - $300,000	26.5%	22.3%	17.8%
$300,000 - $500,000	31.3%	27.7%	26.9%
$500,000 - $1,000,000	0.5%	12.1%	20.9%
$1,000,000 and more	0%	2.7%	7.1%
Owner-occupied households
With a mortgage	57.8%	60.8%	60.6%
Without a mortgage	42.2%	39.2%	39.4%
Median monthly owner costs
With a mortgage	$1,684	$1,987	$1,963
Without a mortgage	$817	$792	$638
Gross rent
Median rent	$1,149	$1,274	$1,413

Education Profile

How educated is the community and how education pays off

Adults with a college degree

14.9%

of adults 25+ with a bachelor's degree or higher

Seneca 14.9%

Illinois 37.8%

United States 35.7%

Adults without a high school diploma

of adults (25+) without a high school diploma

Seneca 6%

Illinois 9.6%

United States 10.4%

School Enrollment

Who is enrolled in school and at what level

School enrollment

603

population (age 3+) enrolled in school

Nursery / Preschool

10.9%

K–12

80.9%

College / Undergraduate

7.5%

Graduate / Professional

0.7%

College-going rate (18-24 yr olds)

20.4%

of 18-24-year-olds in college or graduate school

Seneca

20.4%

Illinois

41.4%

United States

40.9%

Enrollment & school type

Enrollment levels, college-going rate, and public vs private school split

Population 3+ currently enrolled in a school

	Seneca	Illinois	United States
Total enrolled (age 3+)	603	3,051,569	80,089,790
Nursery / preschool	10.9%	6.3%	5.7%
K–12	80.9%	67.3%	67.6%
Kindergarten	17.6%	4.9%	5%
Elementary: Grades 1–4	24%	19.5%	19.8%
Elementary: Grades 5–8	20.7%	20.8%	21%
High School: Grades 9–12	18.6%	22.1%	21.7%
College or graduate school	8.1%	26.4%	26.7%
College, undergraduate	7.5%	19.8%	21%
Graduate, professional school	0.7%	6.6%	5.8%
College-going rate · 18-24 yr olds	20.4%	41.4%	40.9%
School type
Public school	91.7%	80.5%	82%
Private school	8.3%	19.5%	18%

Education Attainment by Level & Gender

What is the highest level of education completed among adults

Education attainment

1,597

population 25 years and over

Total adults (25+)

Less than 9th grade

0.6%

9th-12th, no diploma

5.4%

HS graduate

39%

Some college no degree

23%

Associates degree

17%

Bachelors degree

12.1%

Graduate or professional degree

2.8%

Attainment by gender

Male vs Female

Adults (25+) · Share within each education level

% male · % female

Less than 9th grade

100% · 0%

9th-12th, no diploma

20.7% · 79.3%

HS graduate

55.2% · 44.8%

Some college no degree

53.8% · 46.2%

Associates degree

55.4% · 44.6%

Bachelors degree

49.7% · 50.3%

Graduate or professional degree

40% · 60%

Educational Attainment Overview

Distribution and key education attainment rates for adults (25+)

Highest credential completed · adults 25+

	Seneca	Illinois	United States
Population (25+)	1,597	8,767,004	230,807,303
Less than 9th grade	0.6%	4.6%	4.7%
9th–12th, no diploma	5.4%	5%	5.7%
High school diploma or GED	39%	25.1%	26%
Some college, no degree	23%	19.2%	19.1%
Associate's degree	17%	8.3%	8.8%
Bachelor's degree or higher	14.9%	37.8%	35.7%
Bachelor's degree	12.1%	22.6%	21.6%
Graduate or professional	2.8%	15.3%	14.1%
High School or higher	93.9%	90.5%	89.6%

Earnings by education level

percentage as applicable

Median Earnings

$48,393

Median earnings for adults 25+, by level

Less than HS graduate

$—

HS graduate

$42,250

Some college or associates

$52,000

Bachelors degree

$75,833

Graduate or professional degree

$—

Poverty Rate

3.8%

for ages 25+, with bachelors degree or higher

Less than HS graduate

19.6%

HS graduate

25.4%

Some college or associates

4.4%

Bachelors degree or higher

3.8%

Outcomes by Education Level

Earnings and poverty rates across education levels (25+)

Adults 25+

	Seneca	Illinois	United States
Median earnings
Population 25+, with earnings	$48,393	$55,582	$52,696
Less than high school graduate	$—	$34,655	$32,485
High school graduate (includes equivalency)	$42,250	$40,965	$40,153
Some college or associate's degree	$52,000	$47,813	$47,260
Bachelor's degree	$75,833	$73,326	$70,044
Graduate or professional degree	$—	$91,623	$90,720
Poverty rates
Less than high school graduate	19.6%	21.6%	24.2%
High school graduate (includes equivalency)	25.4%	14.4%	14.4%
Some college or associate's degree	4.4%	9.9%	9.8%
Bachelor's degree or higher	3.8%	4.5%	4.5%

Insights for Seneca, by topic

Income By year By race By age By gender

Population By year By race By age By gender

About Neilsberg Research

Neilsberg Research team are data scientists with expertise in processing, analysis and visualization of big data helping small businesses make right decisions.

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