We got on the river at Riverside Park and went downstream to Irwin Bridge. There was easy access points on both ends and the river was slightly faster in this section than going from Wheeland Park in Riverton to Riverside Park in Springfield. It was about 14 miles taking around 5 hours long. We were not paddling hard and stopped a few times so you could get it done faster. I highly recommending trying this route out, there were old cars stuck to the banks and plenty of wildlife. There were even some sandy banks that you could camp on.
IL waterway sticker
Riverside Park is in Springfield, IL right outside of Sherman and Irwin bridge is out in the country with parking along side the river. Both points can be mapped on Google maps.