This course, a bit outside of Harrisburg, seems to have been a "thing" since at least the late 1990s.  That said, we have little info on past FKTs.

A mix of fire road, single track, rail trail, Horse-Shoe Trail, Appalachian Trail, roots, rocks, leaves, dirt and mud. Start finish is at the same location.

Submitted by Dana Wood:

Founded in 2016, the Lake George 12ster provides a formidable taste of what the Adirondacks have to offer.
Traverse 12 peaks, nearly 40 miles of trails, and up to 9,000 feet of elevation gain
Become a 12ster at your own pace, or tackle them all in a 24-Hour Ultra
Winter and Ultra Winter categories available for those that love to embrace the cold

Vehicles may be used to shuttle between trailheads, or you can do the entire thing "self powered", utilizing a bike ("multisport") or not!

Submitted by Salomon de Casimacker:

L'itinéraire représente la traversée du Massif du Mont Noir, du Camping du Lac des Rouges Truites jusqu'à l'église de Chaux Neuve en passant par le sommet du massif, il emprunte en majeur partie des routes forestières. Plongé dans les sapins et les prairies Jurassiennes le parcours reste rapide et nerveux mais offre malgré tous de très beaux paysages typiques de chez nous. D'une longueur de 22km et 700m de dénivelé positif cette traversée n'attend que vous !  Attention a la faune sauvage (Lynx, Loup et autre gibier et félin)