Stephen Bohn submitted this clever challenge:

"18 loops (or "holes") around the McCabe Golf Course on the Richland Creek Greenway for 50 miles."

Start: Savage River Trail parking lot in Denali National Park. Went up past the rock outcropping to the top of the mountain. Followed the ridge line all the way to Mount Healy. Then went down the mountain on the Mt. Healy Overlook trail. Finish: at the Denali National Park Visitor Center.  Note that the FKT route does not summit Mt Healy, which is technical.

Description from the NPS:

This 12.3 mile loop trail circumnavigates Indian and Celina Lakes in Hoosier National Forest. It is mostly forested and includes several views of the lakes while weaving through hilly hardwood and pine forests. Elevation gain is 1,850' over the loop. The trail is easily accessible from Interstate 64, and makes an inviting midwest trail run with straightforward navigation and no need for shuttling. The Forest Service has a page with further information and maps. They list the trail as 15.7 miles, which would include the connector and other spur trails.

This route combines the Saugatuck Trail and the Aspetuck Trail as described below.  The two together are 18.6 miles one-way.