In the White Mountains, on the high tops, mountain racing is essentially banned by USFS so FKT (fastest known times) are the main way people compete.
One of the classic FKT's is around the Pemigewasset wilderness loop. Its a lovely 31 mile, with 9000ft ascent, around a natural horseshoe.
Having a few days free I trotted around the loop over 2 days, about 10 hours running time, spending the night in Garfield Ridge Shelter.
The FKT is 6:27, by Ben Nephew, with the womens 7:34 by Larris Dannis. I fancy a crack later this year, sub 7 should be very possible.