The wall’s relentlessly smooth face has few cracks to penetrate or nubs to clench. One short section requires a sideways leap, feet and hands off the wall, to holds the size of matchsticks. There are overhangs. Water creeps through some of the few fissures, and ice periodically drops from above. A scale used to gauge difficulty ranks several parts of the Dawn Wall among the toughest to climb in the world.

“People have done single-pitch climbs rated harder,” said the filmmaker Josh Lowell, whose Big Up Productions has chronicled Caldwell’s attempts at the Dawn Wall for years. “But this number of pitches, it’ll certainly be the hardest big-wall climb ever — by a mile.”

Warren Harding and Dean Caldwell (no relation to Tommy) were the first to climb Dawn Wall, in 1970, using ropes and countless rivets over 27 days. Around 2008, Caldwell, from Estes Park, Colo., began to seriously ponder whether the entire length could be free climbed in one push, meaning no relief or rest on the valley floor.

Image After days of climbing, fingers can catch and tear on the rock. Credit... Corey Rich/Aurora Photos

Part of the difficulty of such a quest is the cumulative effect on the mind and body. Climbing for days in a row can rub fingers raw. Sleeping in slings amid the elements can be taxing, if not dangerous.