Wild Horse Island is the largest island in Flathead Lake

Flathead Lake

Flathead Lake is the largest natural freshwater lake in the western part of the contiguous United States. With a surface area of between and , it is slightly larger than Lake Tahoe. The lake is a remnant of the ancient inland sea, Lake Missoula of the era of the last interglacial. Flathead Lake...

, the largest freshwater lake in Montana

Montana

Montana is a state in the Western United States. The western third of Montana contains numerous mountain ranges. Smaller, "island ranges" are found in the central third of the state, for a total of 77 named ranges of the Rocky Mountains. This geographical fact is reflected in the state's name,...

. For centuries, the Salish-Kootenai

Confederated Salish and Kootenai Tribes of the Flathead Nation

The Confederated Salish and Kootenai Tribes of the Flathead Reservation are the Bitterroot Salish, Kootenai and Pend d'Oreilles Tribes. The Flatheads lived between the Cascade Mountains and Rocky Mountains. The Salish initially lived entirely east of the Continental Divide but established their...

 used the 2,100 acre (8.5 km²) island to pasture horses to keep them from being stolen by other tribes. Protected as a state park since 1978, the island near Big Arm Bay is home to abundant wildlife including bighorn sheep

Bighorn Sheep

The bighorn sheep is a species of sheep in North America named for its large horns. These horns can weigh up to , while the sheep themselves weigh up to . Recent genetic testing indicates that there are three distinct subspecies of Ovis canadensis, one of which is endangered: Ovis canadensis sierrae...

, mule deer

Mule Deer

The mule deer is a deer indigenous to western North America. The Mule Deer gets its name from its large mule-like ears. There are believed to be several subspecies, including the black-tailed deer...

, waterfowl

Waterfowl

Waterfowl are certain wildfowl of the order Anseriformes, especially members of the family Anatidae, which includes ducks, geese, and swans....

, bald eagles, and at least three wild horses. Access is by boat only and for day use only. It is managed by the Montana Fish, Wildlife & Parks.