This might be a bit suburban compared to most FKTs. I didn't attempt this with a record in mind, but I am curious now if anyone else has done all or part of the Illinois Prairie Path in one go. Last November 12, 2017, I ran the three main branches (Forest Park to Wheaton, Wheaton to Elgin, and Aurora to Wheaton) in one day, supported by my wife. I started at 6:58am at the Forest Park trail head (or as close as I could figure). Forest Park to Elgin (30mi) took me 5:21:45. (Strava) At Wheaton my wife and I had a leisurely lunch, and then drove to the Aurora trail head. I departed at 1:51pm, and ran Aurora to Wheaton in 2:58:23 (13.4mi). (Strava)
Total time including lunch and driving total out to around 9hrs 51min.