Charles Marshall Pratt was an American rock climber known for big wall climbing first ascents in Yosemite Valley. He was also a long-time climbing instructor and mountain guide with Exum Mountain Guides in the Grand Tetons. Pratt's first experiences were on the scrappy cliffs of Bellingham, Washington's Sehome Hill when he was in high school. In August, 1958, Pratt completed the first ascent of the north face of Fairview Dome in Tuolumne Meadows in Yosemite National Park with Wally Reed, This climb, completed when Pratt was 19, is described as "marvelously direct" and a "memorable climb" in Fifty Classic Climbs of North America. In 1959, he completed the first ascent of the East Face of Washington Column (later called 'Astroman') in Yosemite Valley with Warren Harding and Glen Denny. In 1960, he made the second ascent of The Nose on El Capitan in Yosemite Valley, a route pioneered by Warren Harding in 1958. He climbed with Royal Robbins, Tom Frost and Joe Fitschen, and they made the climb in one continuous push lasting seven days. Robbins said it was "the most magnificent and complete adventure of our lives." The first ascent had taken Harding's team 45 days of climbing spread over an 18-month period. On September 12, 1961, Tom Frost and Royal Robbins began the first ascent of the Salathé Wall on El Capitan, named for pioneer Yosemite climber John Salathé. Pratt was purchasing additional climbing equipment for the ascent during those first few days. Frost and Robbins spent two days establishing the first 600 feet (183 m) of the route, and then retreated to the valley floor, where they met up with Pratt, with whom they spent several more days pushing the route to 1,000 feet (305 m) above the valley floor. Once again, the climbers descended and resupplied. On September 19, they resumed the climb, and after days of intense vertical aid climbing they reached and surpassed "The Roof", a 15-foot (4.6 m) overhang. On September 24, the trio reached the summit. It had taken them a total of 11 days and 36 pitches of vertical climbing to finish the route, which is rated YDS VI, 5.10, A3. In October, 1963, he made the first free ascent of the Kor-Ingalls Route on Castleton Tower near Moab, Utah, with Steve Roper. In the summer of 1964, Pratt, Harding and Yvon Chouinard spent five days in an alpine-style ascent of the South Face of Mount Watkins, located up Tenaya Canyon, a side canyon of Yosemite Valley. The climb was completed in extreme heat with limited water supplies, leading to dehydration of the three climbers. Pratt wrote in the 1965 American Alpine Journal: "By the fourth day, Yvon had lost so much weight from dehydration that he could lower his climbing knickers without undoing a single button. For the first time in seven years, I was able to remove a ring from my finger, and Harding, whose resemblance to the classical conception of Satan is legendary, took on an even more gaunt and sinister appearance." From October 22–31, 1964, with Robbins, Frost and Chouinard, Pratt made the first ascent of the North America Wall on El Capitan, YDS VI, 5.8, A5.