In 1907 he launched on a voyage down the Green and Colorado Rivers in steel-hulled Whitehall boats, but circumstances prevented him from continuing into Grand Canyon. Instead, he towed his boat 165 miles back upstream in the dead of winter. For eight years he placer mined on the banks of the Colorado. In 1916 he left the river and married.
Later that year with Ellsworth Kolb, Loper was the first to boat through Utah’s Westwater Canyon. In the early 1920s he was hired as lead boatman for surveys of the lower Colorado, San Juan, and Upper Green Rivers. To his great disappointment he was not chosen as boatman for the 1923 Grand Canyon survey, and his dream was squelched once again.
In 1939, as Loper neared seventy, a young boatman named Don Harris sought advice on running Grand Canyon. Loper’s advice: Let’s do it together. They launched in July and became one of the first parties to run every rapid. They pledged to do it again ten years hence.
For his return trip in 1949 Loper built a new boat, the Grand Canyon, incorporating design elements of Galloway, Nevills, and his own ideas. He launched on July 7, three weeks shy of eighty years old, leading Don Harris and two other boats. The next day, Loper flipped in 24-1/2-Mile Rapid. Loper was last seen motionless, floating downriver.
That evening they found his boat and dragged it high on the shore near mile 41, where it lies today. A half-century of sun, rain, rockfalls, and tourists have not treated it kindly. What remains is extremely fragile. If you visit it, please do not touch.