Rock Island is a city located in Rock Island County Illinois. It is also the county seat of Rock Island County. With a 2020 population of 36,666, it is the 49th largest city in Illinois and the 1071st largest city in the United States . Rock Island is currently declining at a rate of -0.69% annually and its population has decreased by -6.03% since the most recent census, which recorded a population of 39,018 in 2010. Rock Island reached it's highest population of 51,863 in 1960. Spanning over 17 miles, Rock Island has a population density of 2,173 people per square mile.
The average household income in Rock Island is $62,049 with a poverty rate of 21.09%. The median rental costs in recent years comes to $729 per month, and the median house value is $104,600. The median age in Rock Island is 36 years, 34.8 years for males, and 37.2 years for females.