THE DRILL
To understand what it takes to free a big wall in a day—and why anybody would want to—it helps to look deeper into El Capitan's climbing history, which has involved endless experimentation, the occasional quantum leap, and a basic human need to go faster.

Until Warren Harding came along, climbers essentially ignored El Cap, because its sheer size outstripped their knowledge and tools. But his '58 ascent opened the door, and over the past 50 years, every climbable square foot has been picked over. Another major advance—climbing the Nose in a day—was made by a team of three top climbers moving together up the wall, in 1975. In 1988 came the first free ascent of the Salathé Wall. Another big year was 1993, when Lynn Hill freed all 33 pitches on the Nose.

Caldwell wanted a route that would push him to the limit while pitting him against the clock. "The whole idea of doing something like this in a day seems arbitrary," he admits, but he says there's a sense of history to it, along with a tangible rush that comes from climbing such a big rock so quickly. "There's this buildup of adrenaline, emotion, fear, and excitement," he says. "It's the most intense experience I've found in climbing."

To do Magic Mushroom in less than 24 hours, Caldwell would have to marry his free-climbing skills with speed, organization, and superhuman fitness. To get into peak shape, he returned to a model he'd self-prescribed for the 2005 double day. That year, living in Estes Park, he'd first spent three weeks building a power base, to give himself the muscular "snap" needed to whip through the hardest sequences. He did this by bouldering, either on the overhanging gneiss of Rocky Mountain National Park or on a climbing wall at his parents' house.

Next, he spent a week working on stamina—the ability to pull off hard moves even when pumped. Caldwell then added weight lifting, campusing—arms-only motion up a special dowel board designed to build the upper-body strength needed to nail dynamic precision moves on the rock—and a three-hour, 20-mile, 4,000-vertical-foot bike ride to 12,000 feet. By the end, a full-bore training day involved two hours of bouldering; a drive to a Colorado wall called the Monastery, where Caldwell would hammer out half a dozen climbs between 5.12b and 5.14b; a session in Estes Park's fitness gym; and that evening bike ride.

In California during the winter of 2007–2008, Caldwell flung himself at Yosemite's hardest boulder problems, toughening his skin and strengthening his grip on the blocks' sharp holds. He threw in endurance work at a rhyolite cliff near Sonora, pumping out five or six pitches of 5.13c to 5.14b per day. He used the home gym to perform laps on artificial holds, sling iron, campus, and do pull-ups. He also cycled on the steep, two-lane roads near Yosemite West.

When Sjong came out, in April, Caldwell was almost too ready for a climb that would require slowing down to make a team push. But Caldwell knew that if the team effort worked out, he might just be ready to climb the whole thing in a day.