Robert Edwin Peary (1855-1920), travelling by dog sled and accompanied by Matthew Henson and four Inuit, claimed to have reached the North Pole - a position in the middle of the Arctic Ocean - on April 6, 1909.

Although this was disputed (nobody with him could calculate a geographical position and thereby support his claim), the U.S. Congress nevertheless recognized his achievement in 1911.

In 1990, the National Geographic Society investigated Peary's claim and concluded that he was as close to the Pole as navigational equipment in his time could confirm.

Among other things, they compared Peary's ocean-depth soundings with current information, analysed patterns of ice drift, and applied modern methods of photogrammetry (a process of making measurements from photographs) to his expedition photographs.

Peary's last assault on the Pole began with a force of 89 people (including 69 Inuit) and 246 dogs, and it was not without hardship. The constantly moving and drifting polar ice cap could crack and open up without warning - exposing the icy depths of the Arctic Ocean beneath them. There were several brushes with death.

Upon his return he wrote: "My life work is accomplished... I have got the North Pole out of my system. After 23 years of effort, hard work, disappointments, hardships, privations, more or less suffering, and some risks, I have won the last great geographical prize."