Bison herds were several million strong many years ago, and despite the past excessive hunting, the Montana herd is growing today.
The western movement of the settlers in the 1800s resulted in large-scale hunting of the massive bison herd in North America. An estimated 375,00 bison were killed each year during this time.
They were harvested mostly for their hides and in 1902 there were only about 50 bison roaming around Montana, according to a census conducted by Yellowstone National Park. Until the introduction of the Lacey Act in 1894, which created penalties for illegal killings, bison poaching was difficult to control.
Around this time, conservation of the bison herd in Montana began in Yellowstone National Park and other areas like Niabrara Valley, Nebraska; Wichita Mountains, Oklahoma; and National Bison Range, Montana.
Following these efforts, the U.S. Army began safeguarding the small bison herd in and around Yellowstone National Park in 1918. These early methods of conservation involved culling, feeding, and herding the animals.
In the 1920s the concept of preserving ecological processes, or letting nature take care of things, was introduced in the National Park Service. This notion was formally adopted as a policy in 1967.
Currently the bison herd in Montana and the greater Yellowstone area is approximately 3,000-5,000 in size.
All information gathered from Montana FWP.