Rock Island State Trail is a 19 mile out and back trail located near Peoria, Illinois and is good for all skill levels. The trail is primarily used for road biking and is accessible from April until October.
Great trail for a nice ride. River to Dunlap round trip 25 miles.
For biking I give it a lower rating as it's just too boring. But if you want to go for leasurely bike with someone new to biking that is scared of road and trail it's ok. But it's closer to road then mountain biking.
It's a great place for long runs. I have prepared for marathons and many triathalons on this trail. I prefer starting at Alta and going out so that it's all packed limestone instead of paved and easier on the knees and feet. It's fairly flat and straight so it's not technical.