O'Fallon is a city located in Illinois. With a 2020 population of 29,635, it is the 65th largest city in Illinois and the 1305th largest city in the United States . O'Fallon is currently growing at a rate of 0.09% annually and its population has increased by 4.79% since the most recent census, which recorded a population of 28,281 in 2010. O'Fallon reached it's highest population of 29,635 in 2021. Spanning over 15 miles, O'Fallon has a population density of 1,929 people per square mile.
The average household income in O'Fallon is $105,152 with a poverty rate of 4.28%. The median rental costs in recent years comes to $1,066 per month, and the median house value is $207,900. The median age in O'Fallon is 36.7 years, 35.5 years for males, and 38 years for females.