During the last two million years or so, glaciers of the Great Ice Age formed and disappeared across Minnesota, and the last major advances retreated after blanketing the state with sand, gravel, and boulders. As climate changed, the Wadena lobe melted, retreated north, then advanced southward to a position it held for thousands of years, shaping a field of 1,200 drumlins around Wadena and creating a terminal moraine that forms a major part of the Alexandria Moraine Complex. After shrinking from its maximum position, the Wadena Lobe slowly readvanced to build the massive Alexandria Moraine; though later overridden by other glaciers, its great height and expanse came from this earlier activity. Behind the moraine, ice currents molded the land into about 1,200 streamlined hills of glacial sediment across Otter Tail, Wadena, and Todd counties, their changing alignment recording the radiating flow of the waning lobe, until flow stopped and the debris-filled ice margin collapsed into a broad, hummocky moraine dotted with lakes. Otter Tail County is covered by thick glacial deposits, chiefly in the Alexandria Moraine Complex, with flatter outwash areas in its center, and the state's largest moraine development extends there in a semicircle from Fergus Falls to the south county line, northeast to East Leaf Lake near Deer Creek, and north to Pine Lake east of Perham. The county has more lakes than any other in Minnesota, all associated with ancient glaciers. Inspiration Peak is the tallest of the drumlin hills, rising about 400 feet above the surrounding countryside to about 1,750 feet above sea level, and is the central feature of Inspiration Peak State Wayside Park. Its steep sides provide broad views in three directions, and a quarter-mile winding trail to the summit passes through hardwood forest and opens onto the rolling hills called the Seven Sisters. The panoramic view includes the Leaf Mountains and Christina Lake, the largest migratory layover in Minnesota, whose average depth of 4.5 feet allows aquatic plants to grow and feed waterfowl including canvasbacks, redheads, ringnecks, scaup, coots, geese, and sandhill cranes. The hills that include Inspiration Peak were known to the Ojibwe as Gaskibugwudjiwe, translated by a missionary as Rustling Leaf Mountains. Early pioneers called the peak Leaf Mountain until Sinclair Lewis, the Nobel Prize-winning novelist, shared his love for its enchanted peace and seclusion, after which people began calling it Inspiration Peak; in 1932 the name became official when the site was designated a Minnesota State Wayside.