A classification and brief description with a discussion of high-latitude physiographic processes. Includes maps and photographs. Alaska occupies the great northwestern peninsula of North America, which slopes and drains westward to the Bering and Chukchi Seas. Most of the State is mountainous or hilly although plains 20-100 miles wide abound. The central part, which slopes westward, consists of interspersed plains, plateaus, and rounded mountains, extending from beyond the Canadian border to the west coast; this part is bordered on the north and south by high rugged ranges which effectively cut off the bulk of the peninsula from the Arctic and Pacific Oceans. The northern range is the Arctic Mountains province of the Rocky Mountain System, dominated by the Brooks Range whose summit altitudes are 6,000-8,000 feet. North of this province are the Arctic Foothills, also part of the Rocky Mountain System, and the Arctic Coastal Plain, the northwestern extension of the Interior Plains. The southern mountain barrier, part of the Pacific Mountain System, is a pair of ridges separated by a line of discontinuous depressions, the Coastal Trough province. The northern ridge of the pair is the Alaska-Aleutian province; and the southern, the Pacific Border Ranges province. The highest peaks of North America, rising to an altitude of more than 20,000 feet, are here; and mountains 8,000-12,000 feet in altitude are common.