National Geographic Society has chronicled scientific expeditions, wildlife and world cultures for more than 100 years, amassing 11.5 million photographs and original illustrations.
The Washington-based institution is selling a selection of its archive for the first time. About 240 lots are to be sold at Christie's auction house in New York on December 6. It's expected to bring $3 million.
The archive has 12 000 original pieces of fine art. Highlights in the sale include paintings by N.C. Wyeth and a photo of Admiral Robert Peary's 1908 expedition to the North Pole.
The majority of the works in the sale are by long-time photographers for the magazine.
Proceeds will go for the promotion and preservation of the archive.