Putnam County is the smallest county (by area) in Illinois. According to the 2017 Census of Agriculture, there were 147 farms in Putnam County, spanning 49,760 acres, with an average farm size of 339 acres. The population of Putnam County was 6,006 (based on 2010 census). Putnam County was named after American Revolutionary War General, Israel Putnam. Lee County’s temperatures range from 13°F during January to 86°F during July. Average monthly precipitation ranges from 1.14" during February to 4.32" during August. If you're looking for land for sale in Putnam County, IL, check out Land Pro LLC's current listings below. If there are no current listings in Putnam County, take a look at land for sale in neighboring Bureau County, LaSalle County, and Marshall County. You can also view all the Illinois land offered for sale by Land Pro LLC.