Millbrook is a city located in Kendall County Illinois. With a 2020 population of 324, it is the 1000th largest city in Illinois and the 15036th largest city in the United States . Millbrook is currently declining at a rate of -0.61% annually and its population has decreased by -3.28% since the most recent census, which recorded a population of 335 in 2010. Millbrook reached it's highest population of in . Spanning over 2 miles, Millbrook has a population density of 176 people per square mile.
The average household income in Millbrook is $104,150 with a poverty rate of 15.31%. The median rental costs in recent years comes to $1,038 per month, and the median house value is $252,300. The median age in Millbrook is 36.4 years, 36.9 years for males, and 35.5 years for females.