Jacksonville is a city located in Morgan County Illinois. It is also the county seat of Morgan County. With a 2020 population of 18,267, it is the 137th largest city in Illinois and the 1996th largest city in the United States . Jacksonville is currently declining at a rate of -0.91% annually and its population has decreased by -6.06% since the most recent census, which recorded a population of 19,446 in 2010. Jacksonville reached it's highest population of 21,690 in 1960. Spanning over 11 miles, Jacksonville has a population density of 1,729 people per square mile.
The average household income in Jacksonville is $57,921 with a poverty rate of 16.47%. The median rental costs in recent years comes to $716 per month, and the median house value is $103,900. The median age in Jacksonville is 37.3 years, 34.8 years for males, and 42 years for females.