1874–1970, American arctic explorer, b. Provincetown, Mass., grad. Bowdoin College, 1898, and studied at Harvard. After a decade of teaching, he went on the expedition (1908–9) of Robert E. Peary to the North Pole. Later (1911, 1912) he made ethnological studies among the Labrador Eskimos. Leader of the Crocker Land expedition (1913–17), MacMillan established a base at Etah, Greenland, from which he explored the Greenland coast and Ellesmere and Axel Heiberg islands. By a notable march over the frozen ocean NW of Ellesmere Island he proved the nonexistence of Peary's supposed Crocker Land. His experiences are told in Four Years in the White North (1918, new ed. 1933). He subsequently commanded a number of arctic expeditions and brought back much valuable scientific information. In his polar expedition of 1925 he was accompanied by Richard E. Byrd, who commanded a naval air unit of exploration. For the Field Museum (now the Chicago Natural History Museum) he led expeditions to Greenland, Baffin Island, and Labrador in 1926 and 1927–28. In 1938 he brought back over 40,000 plants from the Arctic. As a member of the U.S. naval reserve, he was recalled to the navy in 1941, made a commander in 1942, and assigned to the hydrographic office in Washington. Later he was placed in command of arctic expeditions in 1944, 1946, and 1947. In the 1944 voyage to Greenland, Baffin Island, and Labrador he made extensive air surveys and brought back some 10,000 photographs. He received the Congressional Medal of Honor that year. Sponsored by Bowdoin College (after which he named his noted exploration ship, the Bowdoin), MacMillan conducted expeditions to Ellesmere Island in 1948 and to Baffin Island in 1949, returning with rare bird specimens and other material. The expedition of 1949 was his 28th voyage of arctic exploration. On a polar trip in 1954, MacMillan and his party barely escaped having their ship destroyed. His other writings include Etah and Beyond (1927) and How Peary Reached the Pole (1934).
- See Arctic Odyssey (1962). ,