YOSEMITE NATIONAL PARK, Calif. — The tip of El Capitan, 3,000 feet above its base, glowed in late-day sunlight while a full moon rose at the other end of the Yosemite Valley on Saturday. In the shadows halfway up the sheer granite face were a pair of dots, the latest to attempt one of rock climbing’s greatest challenges.

There are about 100 routes up El Capitan, first summited from the valley floor in 1958. But these dots, climbers named Tommy Caldwell and Kevin Jorgeson, were trying something that had never been done. They were scaling the Dawn Wall — as smooth as alabaster, as steep as the bedroom wall, more than half a mile tall — without the benefit of ropes, other than to catch their falls.

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Evans said that only about 13 of El Capitan’s climbing routes had been free climbed, meaning that moving upward is done only with hands and feet. The Dawn Wall, so named because its southeast orientation catches the first light of morning, is far harder than any of the others, climbers said.

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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.

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