Back in the late 19th century, the land that is now Wyoming, Montana and the Dakotas were mostly miles and miles of open terrain, punctuated by the settlements of the few intrepid settlers who braved isolation and hostile conditions in hopes of finding adventure and a decent living.

Many who quested out from the east (including the grand adventurer himself, Theodore Roosevelt) came for the beef business. The fenceless open range meant grazing land was easy to come by, so ranchers could own massive herds of cattle. Between 1866 and 1885, around 5.7 million cattle were driven to market or northern ranges, Modern Farmer reports.

Through much of the late 1870s and into the 1880s, cooler summers and mild winters meant that feeding the animals was relatively easy: grass and feed was typically pretty plentiful. But everything changed in the disastrous winter of 1886-1887.

A blazing hot summer had scorched the prairies, so when snow started falling in early November much of the frontier’s livestock were already starving and ill equipped for a hard winter. The problem became a catastrophe when, on January 9, 1887, a blizzard hit, covering parts of the Great Plains in more than 16 inches of snow. Winds whipped, and temperatures dropped to around 50 below.

Few farmers had hay stored for their cattle, so many cows that weren’t killed by the cold soon died from starvation. When spring arrived, millions of the animals were dead, with around 90 percent of the open range’s cattle rotting where they fell.

Those present reported carcasses as far as the eye could see. Dead cattle clogged up rivers and spoiled drinking water. Many ranchers went bankrupt and others simply called it quits and moved back east where conditions appeared less punishing. They called the event “The Great Die-Up,” a macabre play on the term “round-up.”

Ultimately, the disaster altered not just the development of the west, but also the direction of America’s agriculture. Ranchers stopped keeping such gigantic stocks of cattle and began larger farming operations in order to grow food for the animals they had. Most also quit the open range, where livestock could roam far from grain reserves, in favor of smaller, fenced in grazing territories. The winter of 1886-1887 signaled the beginning of the end to the days of roving cowboys and the untamed western wilderness.