Handpicked for the role from a roster of nearly 20 expert climbers and scientists, Jim Whittaker pressed through blizzard-force winds and minus-30-degree air to become the first American to summit Mount Everest. Mr. Whittaker, an REI manager and veteran climber from Seattle, hammered a U.S. flag into the pinnacle of the planet for the first time on May 1, 1963, stoking a national interest in mountaineering that fed the expanding retailer he would later lead as CEO.