The Badger State Trail is a rail trail running from the Illinois-Wisconsin border north to Madison. The route is almost entirely crushed limestone, but is paved for a few miles near the Madison terminus. It features the Stewart tunnel, a 1200-ft tunnel cut through solid limestone. ~40 miles.
--submitted by Mikey Kartje
Note that Mikey Kartje ran *almost* the whole trail in 6h49m18s on 4/5/2020:
"I started at the highway P intersection, which is 1-2 miles north of the IL border terminus of the trail (I think). This appeared to be the most natural starting point, but I could certainly be wrong. I ended where the trail intersects the Southwest Commuter bike path in Madison. Conditions were near-perfect! I think there is a race on this trail, but I am not sure if it runs the entirety of the trail.
My logic at the time was to start at an access point nearest the state border. From the map on the DNR website (attached), it looked like highway P would be a good choice for a starting point. It’s clearly labelled on the map so I thought it would be relatively easy to find. I wasn’t going for an FKT attempt at the time, so I didn’t think too carefully about this. After looking more closely at the WI road atlas and google maps, it looks like there is a road that meets up with the trail at the badger state/jane addams transition (https://goo.gl/maps/DzgteTkKMWrkWVMbA). There seems to be a pretty clear starting point for the badger state trail here."
11/16/2020 Note: The Stewart Tunnel is closed and has been blocked. Until it is reopened, all FKTs must use the official road detour. According to a Comment below, this adds about .4 mi. Do not simply go over the tunnel, as that would be trespassing which is not allowed.
There is a road crossing (State Line Rd) that would be the natural start/end point on the southern end.
Note that as of summer 2020 the Stewart Tunnel is closed for safety concerns because the roof has become unstable. There are two bypass routes around the tunnel that both add mileage but are the only options for the foreseeable future, there is no projected date for reopening the tunnel.
The Tunnel Rd detour for Stewart Tunnel ads around 4/10th of a mile. If I ever ran this route again I would be fine with that.