This is the moment once-endangered bisons are released across a corner of an American plain for the first time in nearly 150 YEARS.

Video shows the massive bulls bolting out of the back of a horse trailer and across the snow-covered plains of Badlands National Park in South Dakota.

More than 30 million bison once roamed North America, but their populations dwindled due to development and hunting.

This is the moment once-endangered bisons are released across a corner of an American plain for the first time - in nearly 150 YEARS. Video shows the massive bulls bolting out of the back of a horse trailer and across the snow-covered plains of Badlands National Park in South Dakota, USA. More than 30 million bison once roamed North America, but their populations dwindled due to Western expansion and hunting. In 1877, it is estimated only 512 plains bison were left.