Grundy County was named after United States Attorney General Felix Grundy. According to the 2017 Census of Agriculture, there were 412 farms in Grundy County, spanning 233,154 acres, with an average farm size of 566 acres. The population of Grundy County was 50,063 (based on 2010 census). Grundy County’s temperatures range from 13°F during January to 85°F during July. Average monthly precipitation ranges from 1.59" during February to 4.16" during June. If you're looking for land for sale in Grundy County, IL, check out Land Pro LLC's current listings below. If there are no current listings in Grundy County, take a look at land for sale in neighboring Kankakee County, Kendall County, LaSalle County, Livingston County, and Will County. You can also view all the Illinois land offered for sale by Land Pro LLC.