Putnam County, Illinois

Putnam County
Location within the U.S. state of Illinois
Illinois's location within the U.S.
Coordinates: 41°12′N 89°17′W / 41.2°N 89.28°W / 41.2; -89.28
Country United States
State Illinois
Founded1825
Named afterIsrael Putnam
SeatHennepin
Largest villageGranville
Area
  Total
172 sq mi (450 km2)
  Land160 sq mi (400 km2)
  Water12 sq mi (30 km2)  7.0%
Population
 (2020)
  Total
5,637
  Estimate 
(2023)
5,561
  Density33/sq mi (13/km2)
Time zoneUTC−6 (Central)
  Summer (DST)UTC−5 (CDT)
Congressional districts14th, 16th
Websitewww.co.putnam.il.us

Putnam County is the least extensive county in the U.S. state of Illinois. According to the 2020 United States census, it had a population of 5,637. The county seat is Hennepin. The county was formed in 1825 out of Fulton County and named after Israel Putnam, who was a general in the American Revolution. Putnam County is part of the Ottawa, IL Micropolitan Statistical Area.