Lacon
- County:
- Marshall County
- County Seat:
- Yes
- Area (mi²):
- 1.6
- State:
- Illinois
Lacon is a city located in Marshall County, Illinois. Lacon has a 2026 population of 1,838. It is also the county seat of Marshall County. Lacon is currently declining at a rate of -0.97% annually and its population has decreased by -1.76% since the most recent census, which recorded a population of 1,871 in 2020.