Approximately 100 bison were released in South Dakota on what is the largest ranch in the US. The project is set to release a total of 1,500 bison in a bid to bring them back to the North America.Approximately 100 bison were released in South Dakota on what is the largest ranch in the US. The project is set to release a total of 1,500 bison in a bid to bring them back to the North America.