IDAHO - A state defined by its rugged wilderness and dramatic "Panhandle," features some of the Pacific Northwest's most impressive inland waters. When identifying the largest lake in Idaho, the answer is a fascinating mix of Ice Age history, military secrets, and massive engineering projects that transformed the Snake River plain.
The Natural Giant: Lake Pend Oreille
Lake Pend Oreille is not only the largest lake in Idaho but also one of the deepest in the United States. Carved by glaciers and the historic Missoula Floods, this "ear-shaped" lake is a cornerstone of the Idaho Panhandle.
- Surface Area: Approximately 148 square miles (roughly 95,000 acres).
- Maximum Depth: 1,152 feet (the 5th deepest in the U.S.).
- Location: Northern Idaho, with primary hubs in Sandpoint and Bayview.
The lake is so deep that the U.S. Navy uses its cavernous waters to test large-scale submarine prototypes, out of sight of prying international satellites. Beyond its military significance, it is a world-class destination for anglers seeking giant "Kamloops" rainbow trout and hikers exploring the steep, forested shorelines of the Cabinet and Bitterroot mountains. Much of the southern shore remains wild, protected within the 4,000-acre Farragut State Park.
The Man-Made Workhorse: American Falls Reservoir
While Lake Pend Oreille dominates the north, the American Falls Reservoir is the largest artificial body of water in the state by surface area. It is a vital link in Idaho's irrigation system, supporting the State famous agricultural industry.
- Surface Area: Approximately 87 square miles (56,000 acres).
- Shoreline: Over 100 miles.
- Location: Southeastern Idaho, near the city of Pocatello and the town of American Falls.
The creation of this reservoir in the 1920s was so significant that the entire original town of American Falls had to be relocated to higher ground. Today, it is the third-largest lake in the state. While it lacks the extreme depth of the northern glacial lakes, it is a premier spot for birdwatching and ice fishing, providing a wide, expansive water landscape in the middle of the high-desert lava plains.
Idaho's water landscape is anchored by Lake Pend Oreille in the north, a natural glacial wonder that holds the title of the State largest and deepest lake, famous for its submarine testing grounds and alpine beauty. To the south, the American Falls Reservoir serves as the State largest artificial lake, a massive expanse of the Snake River that powers local agriculture and provides a sprawling sanctuary for migratory birds and local anglers.