Assigned to the Nicaragua Ship Canal survey in 1884 as assistant engineer, he invented a rolling lock gate and was promoted to director in 1887–1888.
Meanwhile, in 1886, he led the first of eight expeditions to the Artic; on 6 April 1909, following a final dash of 130 miles in five days, he, fellow explorer Matt Henson and four Eskimos reached the North Pole over the ice. (Whether or not they succeeded was disputed for some years until the Navigation Foundation examined shadows in a photo they took, which demonstrated that—within the accuracy of their instruments—they did reach the pole.)
Promoted rear admiral, Peary received the thanks of Congress 30 March 1911; he also received honors from numerous scientific societies of Europe and America and wrote several books on his experiences.
He died at Washington, DC, 20 February 1920.