History of the Flathead Lake Monster

Something mysterious may be lurking in the depths of Flathead Lake! Many locals believe in the existence of a Flathead Lake Monster, with tales of the creature originating with the Kootenai tribe and continuing with numerous documented sightings throughout the years. Here is a history of the Montana mythical creature that has captured the community’s imagination:

The Legend

Within Kootenai folklore, there is a story of a huge monster with antlers that resides in the middle of the lake. When the tribe was attempting to cross the frozen lake on foot, two girls discovered the antlers protruding out of the ice and tried to take them. The monster rose up, breaking the ice and causing half of the tribe to drown in the water. Early white settlers also regularly claimed to see something unusual in the lake. 

In 1889, while crossing Flathead Lake, the captain of a steamboat and his 100 passengers reported witnessing an unusually large, whale-like creature in the water. Numerous sightings by a variety of people, from local fishermen to tourists, have been recorded since. The Flathead Lake monster is nicknamed “Flessie” after Loch Ness’s famous “Nessie.” Descriptions of the creature vary, with some claiming it is long like an eel or serpent, while others say it resembles a large fish or small whale. Sightings seem to be more frequent on the southern end of the Lake.

Alternative Explanations and Attempts to Find the Monster

Skeptics of the Flathead Lake Monster have offered several theories about what it might be. Some think it is an undiscovered aquatic species such as a giant eel, huge prehistoric fish, or possibly swimming land animals such as horses, bears, or elk. Others suggest the sightings could be explained by floating logs or illusions cast by shifting light in the waves. 

Hoping to capture or better understand the Flathead Lake Monster, Big Fish Unlimited began offering cash prizes for large catches in the 1950s. An angler named C. Leslie Griffith presented a massive 90-inch-long white sturgeon that weighed 181 pounds, leading some to speculate that “Flessie” is just a large sturgeon. However, an analysis of the fish’s stomach contents indicated the sturgeon might have originated elsewhere, and there have been no similar catches in the Flathead since. The sturgeon is on display at the Polson-Flathead Historical Museum. The largest uncontroversial catch out of Flathead Lake is a lake trout that weighed 42 pounds, 8 ounces and measured 44 inches in length, which was caught in 1999.

Modern Influence

Today, residents and visitors alike continue to seek the Flathead Lake Monster, with some even claiming to have spotted it, and you may even be able to find “Flessie” themed t-shirts, trinkets, and other memorabilia at gift shops around the area. On Go Sail Flathead Lake’s sailboat tours, our knowledgeable captains are familiar with every corner of the lake and can tell you all its secrets and stories. If you want to search for Flessie or spend the day fishing, you can rent a sailboat for self-guided exploration and see if you can catch a Flathead Lake Monster yourself!