[mauvehaus]

Some US additions that don't appear to have been suggested elsewhere: AT, PCT, CDT, which collectively make up the triple crown of North American long-distance hiking. All easily googleable by acronym.

Less famous: the North Country Trail, Florida Trail, Hayduke Trail, Buckeye Trail, Benton McKaye Trail, Mountains to Sea Trail. And of course the Long Trail.

[mauvehaus]

Replying to self with some long distance non hiking trails:

Northern Forest Canoe Trail (I hope it is self explanatory how one is expected to travel this trail)

Catamount Trail (cross country ski)

Kokopelli Trail (mountain bike)

[dugmartin]

Thanks for letting me know about the Catamount Trail! I've lived 15 miles from the start of the southern end of it for 17 years and this is the first I've heard of it.