There has been some dispute over this one: The credit usually goes to American explorer and former naval officer Robert E. Peary (1856–1920), who, after several tries, reached the North Pole by dogsled on April 6, 1909, along with Matthew A. Henson and three Inuit companions. Unbeknownst to him, five days before this achievement, another American explorer, Dr. Frederick Cook (1865–1940), claimed that he had reached the North Pole a year earlier. Peary and Cook knew each other: Cook had been the surgeon on the Peary Arctic expedition of 1891 to 1892, which reached Greenland. And for his part, Cook’s claim was investigated by scientists, but the evidence he supplied did not substantiate the claim. Thus, Peary was recognized as the first to reach the northern extremity of Earth’s axis.