Porter was in charge of astronomical observations on the Ziegler Polar Expeditions financed by New York businessman William Ziegler in 1901 and 1903. The second expedition was stranded in the arctic for 3 years when their ship, the Steam Yacht America, was crushed by the ice and sank in Teplitz Bay off Rudolf Island in the Russian arctic. In 1906 Porter again joined Frederick Cook in an expedition to Alaska's Denali. Porter's party surveyed a region around the mountain (including painting a watercolor of the mountain) while Cook's party broke off to climb the mountain. When the parties rendezvoused, Porter was skeptical of Cook's claims that he climbed the mountain.