Putnam County is the smallest county in the state of Illinois, encompassing only 166 square miles. Putnam County's courthouse in Hennepin, the county seat, is located on the bluffs above the Illinois River and is the oldest courthouse currently in use in Illinois which has been maintained in an original form. The courthouse was built in 1839, the year Putnam County's present-day boundaries were established. The Pulsifer House was built in 1844 in Greek Revival style-architecture. It's on the National Historic Register and is home to the Putnam County Historical Society.

Western Putnam County was home to the Pottawtomi Tribe until the early 1830's. Chief Senachwine is buried in Putnam County.

The Putnam County Ag Museum is east of the Pulsifer House at 501 Old Hwy 26. It is the home of antique farm equipment, a permanent exhibit on the history of corn in the United States, a permanent exhibit on the Illinois River and area wildlife and many other exhibits too numerous to mention. While the county may be small there are many things to do and see in Putnam. Explore Putnam County today.