Up & down:  Start at the Granite Flats Trailhead. Follow the Deer Creek/Dry Creek Trail to the high meadow. Turn left at junction in meadow onto trail toward Box Elder Peak (11,101').

Submitted by Sam Linnet:

This is a 9 mile rail trail that goes from Newport to Claremont, https://www.nhstateparks.org/visit/recreational-rail-trails/sugar-river-recreational-rail-trail. 

Note that the west end of the trail has a clear dead end as shown on our map, but some maps show it continuing to Charlestown Road in Claremont.  We're not sure what's up with that, but for now the FKT route is as shown.