North Pole, the earth’s northernmost point. It is located at the northern end of the earth’s axis, an imaginary line through the center of the earth around which the earth revolves. It is also the northern center from which all the meridians of longitude begin. From the North Pole, all directions on the earth’s surface are south. The North Pole lies in the Arctic Ocean and is usually covered with pack ice.

An American expedition led by Robert E. Peary was the first that is generally credited with reaching the North Pole, arriving there on April 6, 1909. Peary was accompanied by his assistant, Matthew A. Henson, and four Inuit. There is some evidence that they may have missed the pole by a few kilometers. Richard E. Byrd and Floyd Bennett are credited with making the first airplane flight over the pole, although there is some controversy as to whether they too missed the mark. In 1958 the United States atomic submarine Nautilus became the first submarine to pass under the ice at the pole.

In addition to the geographic north and south poles, the earth has magnetic poles. The north magnetic pole is located in the area of Bathurst Island, Canada. The north magnetic pole, rather than the geographic pole, is the actual point that is indicated by the magnetic compasses used in navigation. It is more than 1600 km (1000 mi) from the geographic North Pole, and because of this discrepancy, magnetic compass readings must be corrected by a factor called declination. The position of the north magnetic pole moves over time, requiring the declination factor to be updated from time to time. A newer navigation device, the gyrocompass, points to the geographic North Pole and thus does not need this compensating factor.