Courthouse, Pike County, Illinois. Is part of the NRHP-listed Pittsfield Historic District. – Mingusboodle at English Wikipedia, Public domain – Wikimedia Commons Pike County is located in Illinois. The region is located on the bodies of water Mississippi River and Illinois River. About 15,989 people live here. Between 2010 and 2020, the population declined from 16,430 to 14,739. The area covers about 2,199.0 square kilometers. The region is divided into 18 Municipalities. The region was founded in 1821. The name originates from Zebulon Pike (American military officer) Pike County is county in Illinois, United States. More information at www.pikecountyil.org.