Hennepin is a city located in Putnam County Illinois. It is also the county seat of Putnam County. With a 2020 population of 703, it is the 750th largest city in Illinois and the 11866th largest city in the United States . Hennepin is currently declining at a rate of -0.14% annually and its population has decreased by -7.13% since the most recent census, which recorded a population of 757 in 2010. Hennepin reached it's highest population of in . Spanning over 6 miles, Hennepin has a population density of 132 people per square mile.
The average household income in Hennepin is $70,379 with a poverty rate of 10.50%. The median rental costs in recent years comes to $713 per month, and the median house value is $152,000. The median age in Hennepin is 47.7 years, 47.1 years for males, and 48.5 years for females.