Bison Reintroduction Timeline

Our growing and healthy bison herd is the result of a decade of dedication and hard work by collaborators, scientists, veterinarians, donors, and staff.

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At a glance, here's how the herd has progressed:

Year Number of Bison Source
2005 16 Wind Cave National Park, SD
2006 20 Wind Cave National Park, SD
2007 22 Wind Cave National Park, SD
2008 10 TNC Broken Kettle Grasslands Preserve, IA
2010 93 Elk Island National Park, Edmonton, Alberta
2012 72 Elk Island National Park, Edmonton, Alberta
2014 73 Elk Island National Park, Edmonton, Alberta

2005: First Bison Introduced to American Prairie

On a cold and rainy night, not long past midnight on October 20, 2005, 16 bison stepped back onto the Montana prairie after an absence of more than 120 years. APR and World Wildlife Fund staff watched as the bison began to graze in their holding pasture, acclimating to their new home before being turned out onto American Prairie. Several of these bison were pregnant cows. After much waiting, the American Prairie Reserve Manager was proud to report the births of five baby bison on the prairie in April 2006.

2006-2009: A Growing Herd

From 2006 to 2009, the herd continued to grow with the addition of new arrivals from Wind Cave National Park and The Nature Conservancy of South Dakota. Additional calves have been born on American Prairie each spring since 2006.


In early 2010, we greatly increased the size of our herd with the addition of 94 bison from Elk Island National Park in Alberta, Canada. The ancestors of these bison originally came from Montana and were part of the Pablo herd, the largest herd of bison left in North America in the early 1900s, after they were largely extirpated from the Great Plains. The Pablo herd was privately owned until the Canadian government purchased the bison in 1907. The return of these bison to Montana continues to be a historic homecoming – 71 additional bison calves were transferred from Elk Island to American Prairie in early 2012 and another 73 calves were relocated in early 2014.


With rapid population growth of the herd, we knew we would quickly reach the carrying capacity of the Sun Prairie unit and started the Environmental Assessment process to expand the bison herd onto the Bureau of Land Management (BLM) allotments. The carrying capacity of Sun Prairie was reached in early 2016. While going through the Environmental Assessment process with the BLM, we expanded the herd to the deeded portion of the Sun Prairie North unit in early 2016. In 2017 and 2018, we also expanded the herd onto the deeded portions of the Dry Fork and White Rock units. During these expansions, a portion of the surplus bison were distributed to Tribal, Agency and other conservation partners marking the first time that a large number of American Prairie bison were able to be distributed to start new herds and improve the genetics of others.


American Prairie owns private properties tied to BLM grazing allotments. We first submitted a proposal to graze bison on these public land allotments in 2017, and then submitted a reduced application in 2019. After years of comprehensive analysis and thousands of public comment, the BLM gave final approval to American Prairie to graze bison across 63,500 acres of federal public lands in Phillips County in July 2022.

The BLM’s Environmental Analysis (EA) and final Record of Decision (ROD) concluded that American Prairie’s grazing application would have no significant impact on the land or local cattle ranching economy. The EA predicts the decision will benefit local wildlife, improve land and water quality, and create new jobs. However, the Montana Stockgrowers Association, the Montana Attorney General and the Governor’s Office filed appeals seeking to stop the decision from being implemented and the issue is currently being litigated in the Department of Interior’s Office of Hearings and Appeals.

We are proud to continue to distribute bison to tribal and conservation partners, and to exchange bison with nearby tribes. With an eye to the future, we are also reassessing and developing our long-term vision for bison expansion, genetic diversification, and public benefit at American Prairie.

Other Bison Restoration Projects & Programs

Nationwide Conservation

Bison Harvest