OFallon, IL Profile: Facts & Data


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OFallon, Illinois - Basic Facts

The City of O'Fallon had a population of 30,261 as of July 1, 2018. OFallon ranks in the upper quartile for Population Density and Diversity Index when compared to the other cities, towns and Census Designated Places (CDPs) in Illinois. See peer rankings below.

The primary coordinate point for OFallon is located at latitude 38.6 and longitude -89.9155 in St. Clair County. The formal boundaries for the City of O'Fallon (see map below) encompass a land area of 14.85 sq. miles and a water area of 0.12 sq. miles. St. Clair County is in the Central time zone (GMT -6). The elevation is 548 feet.

The City of O'Fallon (GNIS ID: 2395302) has a C1 Census Class Code which indicates an active incorporated place that does not serve as a county subdivision equivalent. It also has a Functional Status Code of "A" which identifies an active government providing primary general-purpose functions.

The City of O'Fallon is located within Township of O'Fallon, a minor civil division (MCD) of St. Clair County.

Beneath the boundary map are tables with OFallon population, income and housing data, five-year growth projections and peer comparisons for key demographic data. The estimates are for July 1, 2018.

Jump to... (On This Page!)
  1. OFallon 2018 Demographic Data
  2. Growth Rates for OFallon (Historical & 5-Year Forecast)
  3. Peer Comparisons (Rank and Percentile)
  1. Neighborhoods Demographics (Home Values, Household Income, etc.)
  2. Illinois Research Tools (Easy Tools & Current Data)
  3. Illinois Data Comparison Tool - 2018 Demographics

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OFallon, IL Data & Demographics (As of July 1, 2018)


Total Population 30,261
Population in Households 30,223
Population in Familes 25,724
Population in Group Qrtrs 38
Population Density2 2,037
Diversity Index3 45


Median Household Income $82,009
Average Household Income $102,952
Per Capita Income $39,785


Total Housing Units 12,010 (100%)
Owner Occupied HU 7,693 (64.1%)
Renter Occupied HU 3,743 (31.2%)
Vacant Housing Units 574 ( 4.8%)
Median Home Value $197,988
Average Home Value $238,887


Total Households 11,436
Average Household Size 2.64
Family Households 8,070
Average Family Size 3
  1. Demographics are point estimates for July 1st of the current year and each for the forecast years. See References for more information.
  2. Population Density = Total Population per square mile.
  3. The Diversity Index is a scale of 0 to 100 that represents the likelihood that two persons, chosen at random from the same area, belong to different race or ethnic groups. If an area's entire population belongs to one race AND one ethnic group, then the area has zero diversity. An area's diversity index increases to 100 when the population is evenly divided into two or more race/ethnic groups.


2010-2018 2018-2023
Population 0.7% 0.12%
Households 0.65% 0.11%
Families 0.27% 0.0%
Median Household Income   1.62%
Per Capita Income   2.2%

OFallon, IL - Peer Comparisons by Rank and Percentile

The table below compares OFallon to the other 1,368 incorporated cities, towns and CDPs in Illinois by rank and percentile using July 1, 2018 data. The location Ranked # 1 has the highest value. A location that ranks higher than 75% of its peers would be in the 75th percentile of the peer group.

Variable Description Rank Percentile
Total Population # 66 95th
Population Density # 266 81st
Diversity Index # 217 84th
Median Household Income # 162 88th
Per Capita Income # 155 89th

Additional comparisons and rankings can be made with a VERY EASY TO USE Illinois Census Data Comparison Tool.

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Compare Illinois July 1, 2018 Data
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