Putnam County, Illinois in the context of Ottawa, IL Micropolitan Statistical Area

There are 102 counties in Illinois. The most populous of these is Cook County, the second-most populous county in the United States and the home of Chicago, while the least populous is Hardin County. The largest by land area is McLean County, while the smallest is Putnam County. Illinois's FIPS state code is 17 and its postal abbreviation is IL.

What is now Illinois was claimed as part of Illinois County, Virginia, between 1778 and 1782. Modern-day county formation dates to 1790 when the area was part of the Northwest Territory; two counties — St. Clair and Knox — were created at that time. Knox would later become a county in Indiana and is unrelated to the current Knox County in Illinois, while St. Clair would become the oldest county in Illinois. Successive territorial governments created 15 counties by the time Illinois achieved statehood in 1818. The last county created in the state, Ford County, was created by the Illinois government in 1859.

The Sue and Wes Dixon Waterfowl Refuge is a 3,100-acre riverine wetland in Putnam County, Illinois. Located just south of the county seat of Hennepin, it occupies the former site of Hennepin Lake and adjacent Hopper Lake. The reclaimed wetland is a Ramsar treaty site, a wetland of international importance.

LaSalle County is a county located within the Fox Valley and Illinois River Valley regions of the U.S. state of Illinois. As of the 2020 Census, it had a population of 109,658. Its county seat and largest city is Ottawa. LaSalle County is part of the Ottawa, IL Micropolitan Statistical Area of Northern Illinois.

LaSalle County borders Woodford, Marshall, Putnam, Bureau, Livingston, Lee, DeKalb, Kendall, and Grundy counties. Though LaSalle County is in the Chicago media market, it retains a unique identity with a mix of river towns and vast expanses of farmland. The county lies at the intersection of the Chicago, Peoria, Quad Cities and Rockford television markets with all four regions broadcasting within its borders and having a strong influence on the area, despite the county being only 60 miles (97 km) southwest of Chicago.

Hennepin is a village located on the Illinois River in Putnam County, Illinois, United States. The population was 757 in 2010, an increase of 50 since the 2000 census. It is the county seat of and the second largest village in Putnam County.

Hennepin is part of the Ottawa Micropolitan Statistical Area.