
Ottawa
- County:
- LaSalle County
- County Seat:
- Yes
- Area (mi²):
- 14.895
- State:
- Illinois
Ottawa is a city located in LaSalle County, Illinois. Ottawa has a 2025 population of 18,691. It is also the county seat of .Ottawa is currently declining at a rate of -0.16% annually and its population has decreased by -0.81% since the most recent census, which recorded a population of 18,843 in 2020.
The average household income in Ottawa is $92,222 with a poverty rate of 14.44%. The median age in Ottawa is 40.3 years: 39 years for males, and 42.3 years for females.