WEBIn 2021, Will County, IL had a population of 696k people with a median age of 38.3 and a median household income of $95,751. Between 2020 and 2021 the population of Will County, IL grew from 689,704 to 696,403, a 0.971% increase and its median household income grew from $90,800 to $95,751, a 5.45% increase.