Jason Wolfe submitted the route:

Starts at the town of Cameron, AZ. Run, boulder, ford.. etc through the Little Colorado River Gorge. Exit via the Salt Trailhead > This an EXTREME route that has to be done at the right time of year, with the right gear, and the right amount of backcountry knowledge.
 

The Seneca Creek Greenway Trail (SCGT) is a nearly 30 mile trail in Montgomery County, MD. The aim of the trail is to connect the Potomac and Patuxent rivers. It stretches from Riley's Lock on the C&O Canal and follows blue blazes, overlapping with several other trail system, and end indiscreetly in a neighborhood near Damascus High School. The trail does not currently make it the entire way to Patuxent River State Park.

The European long-distance hiking trail E1 starts at the North Cape in Norway. It crosses Finland, Sweden, Denmark, Germany and Switzerland over a distance of around 7000 km until it finally reaches Salerno via Italy.
This route covers the German section of the E1 from Flensburg to Konstanz is described. It is about 1900 km long and is officially divided into 76 stages.

NOTE: Prior to April 2021 people took different routes traversing the park, and the FKTs reflect that.  Then, Patrick Blair very meticulously worked out the best routes for the one-way (31 miles) and out & back (actually a compressed loop with some overlapping sections, 62 miles).  From now people should carefully follow Patrick's routes if they wish to contest the FKT.  Note also that some of the previous FKTs were on longer routes, so it's not really an apples-apples comparison.

Mid Sussex Link (55km):  Brighton & Hove, E Sussex, W Sussex