On an August night in Yellowstone country, campgrounds, vacation cabins, and roadside camps along Hebgen Lake and the Madison River were full when, a few minutes before midnight, a magnitude 7.5 earthquake struck and violently jolted the earth. People emerged from tents, cars, and cabins to find trees thrashing, dust clouds rising, and chaos in the night. The largest earthquake recorded in the Rocky Mountains, it killed 28 people, trapped over 250 in Madison Canyon, and left hundreds more grieving loved ones or friends or facing damage to homes and businesses. At 11:37 p.m. on August 17, 1959, fault scarps formed, Hebgen Lake began to slosh back and forth, waves overtopped the dam and damaged lakeside buildings, and destabilized shorelines slid into the lake, taking parts of Highway 287. Minutes later, an 80-million-ton landslide blocked the Madison River and cut off the exit road for campers. From midnight to dawn on August 18, Earthquake Lake rose rapidly and swallowed campsites as aftershocks continued, while people scrambled for safety, rescued the stranded, tended to the injured, and, fearing Hebgen Dam would break, headed for high ground. From dawn to noon, helicopters and planes scanned the wreckage and reported the damage, and just before noon Forest Service smokejumpers parachuted in to assist trapped campers and prepare an evacuation. From noon to 3:00 p.m., the most gravely injured were evacuated, and by dusk the remaining refugees began leaving the area on an emergency bypass road along Hebgen Lake as rescue workers continued searching the canyon campsites.