On February 19, 1847, the first rescuers reach surviving members of the Donner Party, a group of California-bound emigrants stranded by snow in the Sierra Nevada Mountains.

In the summer of 1846, in the midst of a Western-bound fever sweeping the United States, 89 people—including 31 members of the Donner and Reed families—set out in a wagon train from Springfield, Illinois. After arriving at Fort Bridger, Wyoming, the emigrants decided to avoid the usual route and try a new trail recently blazed by California promoter Lansford Hastings, the so-called “Hastings Cutoff.” After electing George Donner as their captain, the party departed Fort Bridger in mid-July.

The shortcut was nothing of the sort: It set the Donner Party back nearly three weeks and cost them much-needed supplies. After suffering great hardships in the Wasatch Mountains, the Great Salt Lake Desert and along the Humboldt River, they finally reached the Sierra Nevada Mountains in early October. Despite the lateness of the season, the emigrants continued to press on, and on October 28 they camped at Truckee Lake, located in the high mountains 21 kilometers northwest of Lake Tahoe. Overnight, an early winter storm blanketed the ground with snow, blocking the mountain pass and trapping the Donner Party.

Most of the group stayed near the lake–now known as Donner Lake–while the Donner family and others made camp six miles away at Alder Creek. Building makeshift tents out of their wagons and killing their oxen for food, they hoped for a thaw that never came. Fifteen of the stronger emigrants, later known as the Forlorn Hope, set out west on snowshoes for Sutter’s Fort on December 16. Three weeks later, after harsh weather and lack of supplies killed several of the expedition and forced the others to resort to cannibalism, seven survivors reached a Native American village.

News of the stranded Donner Party traveled fast to Sutter’s Fort, and a rescue party set out on January 31. Arriving at Donner Lake 20 days later, they found the camp completely snowbound and the surviving emigrants delirious with relief at their arrival. Rescuers fed the starving group as well as they could and then began evacuating them. Three more rescue parties arrived to help, but the return to Sutter’s Fort proved equally harrowing, and the last survivors didn’t reach safety until late April. Of the 89 original members of the Donner Party, only 45 reached California.

READ MORE: Ten Things You Should Know About the Donner Party