The Douglas State Trail is a 12.5 mile mixed use trail running between Rochester and Pine Island, Minnesota, with an intermediate trailhead in Douglas, MN (about 4.5 miles from Rochester).
 

-submitted by Nick Loyal

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:

Hancock, MD is home to the narrowest pinch in the state. Barely 2.5 miles wide. This route is all on roads, and is slightly uphill if you travel northbound. There is a Strava segment for the route where times can be compared.

https://www.strava.com/activities/840939567/overview

- Submitted by Evan Daney

A technical route starting by the Emosson dam (Switzerland), finish in Servoz (France).