Wood Buffalo National Park is the largest national park of Canada at 44,741 km2. It is in northeastern Alberta and the southern Northwest Territories. Larger in area than Switzerland, it is the second-largest national park in the world. The park was established in 1922 to protect the world's largest herd of free-roaming wood bison. They became hybridized after the introduction of plains bison. The population is currently estimated at 3,000.