The Rock Island State Trail is a "rails-to-trails" route owned by the state of Illinois. Its southern trailhead is at Alta, Il. just north of Peoria,Il. The Northern terminius is in the farm community of Toulon, Il. It is a 25 mile crushed limestone and dirt trail similiar to the trail used in the Tunnel Hill 100 mile race. The trail is very scenic passing through historic farm communities of Dunlap, Princeville, Wyoming and Toulon, Il. The trail in the spring and summer months is lined with many types of wild flowers and crosses a number of creeks including the famed Spoon River. Some areas of the trail will have areas of mud and standing water after a spring rain.
More information about the Rock Island State Trail can be found at: https://www2.illinois.gov/dnr/Parks/Pages/RockIslandTrail.aspx
Note: Some sources such as AllTrails describe the Trail as being 38 miles long. This isn't accurate. The Rock Island State Trail is 25 miles in length while the co-joined Rock Island Greenway owned and operated by the Peoria Park District is 13 miles. It is a paved primarily bike path from downtown Peoria to the Rock Island State Trail head in Alta, Il.
Endpoint notes from Marlin Weekley:
The beginning of the trail is in Alta, Il. There is a sign announcing the trailhead and the trail surface obviously starts by this sign. You can access the trail from a nice parking lot with pit toilets about 0.2 from the trailhead. It would be easy to think this is the beginning of the trail. Users should look for red/white mile marker 0 near the beginning of the trail. The northern terminus at Toulon simply dead ends into grass surrounding a business. There are signs identifying the Trail and a red/white mile marker 24.7 near the trailhead. The Toulon Public library is across the street. The signage explains to trail users there is public water, restrooms and bike tools there. 0.2 of a mile from the Toulon trailhead is a nice parking lot and pit toilets for trail users.