The park officially became a national park on 19 February 2001. This was because of the Canada National Parks Act. In 2006, some of the plains bison that lived in Elk Island National Park in Alberta were moved to Grasslands National Park. This was important because many of the bison in Canada were killed in the 1800s. It was the first time that plains bison were on the shortgrass prairies of Canada since the 1890s. 71 bison were first moved to the park. Nine years later, in 2015, there were 310 bison. There are now plains bison at other national parks in Canada.