From Wikipedia

The Donner Party

The Donner Party (sometimes called the Donner-Reed Party) was a group of American pioneers who set out for California in a wagon train. Delayed by a series of mishaps, they spent the winter of 1846–47 snowbound in the Sierra Nevada. Some of the emigrants resorted to cannibalism to survive, eating those who had succumbed to starvation and sickness.

The journey west usually took between four and six months, but the Donner Party was slowed by following a new route called the Hastings Cutoff, which crossed Utah's Wasatch Mountains and Great Salt Lake Desert. The rugged terrain, and difficulties later encountered while traveling along the Humboldt River in present-day Nevada, resulted in the loss of many cattle and wagons, and led to divisions within the group.

By the beginning of November 1846 the emigrants had reached the Sierra Nevada, where they became trapped by an early, heavy snowfall near Truckee (now Donner) Lake, high in the mountains. Their food supplies ran low, and in mid-December some of the group set out on foot to obtain help. Rescuers from California attempted to reach the emigrants, but the first relief party did not arrive until the middle of February 1847, almost four months after the wagon train became trapped. Of the 87 members of the party, 48 survived to reach California.

Historians have described the episode as one of the most spectacular tragedies in Californian history and in the record of western migration.