Bison once numbered in the hundreds of millions and roamed in vast herds throughout North America. But after Europeans colonized and began developing the continent, the newcomers set about killing the shaggy herbivores en masse. Their numbers declined rapidly, and, by the 1870s, American bison—also called buffalo—had nearly gone extinct, dropping to a total population of around 500.

But bison are survivors. They hung on in a small herd in what’s now Yellowstone National Park, as well as another tiny population in Canada. A handful of ranchers also kept some alive, most of whom also experimented with breeding buffalo and cattle in a failed attempt to create a better beef-producing animal.

More than a century’s worth of dedicated conservation has helped the