On Sunday, March 23, 2020, I ran the Chicago Lakefront Trail from north to south and back in 3:54:14. I started exactly at 6am and was only running in darkness for a few miles before the sun rose. The day was cold but not freezing, with temps peaking in the mid-30s. There was a gentle south wind, so I was running into it during the first half of the run and had it at my back during the latter stretch. The water fountains had not yet been turned on, but I stored gels and bottles at the southern terminus the night before and considering the colder temps, I did not need any additional fluid. I was able to maintain a pretty consistent pace and even negative split the effort, due in part to the tailwind.
I attempted to retrace the exact same route that Rich took in 2016 with two exceptions: at Monroe, the path now arcs out to the east and curves back instead of directly crossing the road, adding about a 5th of a mile. And near Navy Pier, a pedestrian bridge has been built to the west of Lake Point Tower—the trail no longer bends around the building. Between the two deviations, the distance more or less nets out. There were also a few spots where short portions of the pedestrian trail were closed due to construction or water damage and were detoured to the bike path. But said detours were so minimal and brief as to not significantly add or subtract distance.
In line with Rich's observation, the trail markers indicate that the length of the Chicago Lakefront Trail is 18 miles one way; however, my watch showed it being just short. Round trip, my Garmin clocked it at 35.75 miles.
This is an incredibly fun if not slightly monotonous run that's flat and fast enough to cater to speedsters, but long enough to still require serious endurance. I believe there is still lots of room for the record to drop, especially if done supported.