From traillink.com:

The Blackwater Canyon Trail follows one of the most challenging and picturesque segments of the former West Virginia Central & Pittsburgh Railway. On its 10.7-mile run deep through the Monongahela National Forest in eastern West Virginia, the rough dirt trail passes waterfalls and relics of the railroad and coal industries.

Located in Sleeping Bear National Lakeshore, this is arguably the premier sand dune climb in North America! The FKT Route is 10 laps up/down (or down/up).  The vert on this compares favorably with other iconic hillclimbs, even in the mountainous west, yet this route offers a swim in a huge blue lake at the bottom and the joy of running downhill in soft white sand.  This is a popular and contested Strava segment, and really worth doing, regardless of your time.