Flathead Lake Facts

Nestled in the scenic northwest corner of Montana, Flathead Lake is a true natural wonder. Known for its vast size, clear waters, and recreational opportunities, it’s not just a regional gem but also a standout on the national map. Whether you’re a nature enthusiast, a curious traveler, or a local resident, learning about Flathead Lake adds depth to every visit.

Here’s a comprehensive look at the most fascinating, fun, and informative facts about Flathead Lake.

1. Flathead Lake is the Largest Natural Freshwater Lake West of the Mississippi

Flathead Lake holds the title of the largest natural freshwater lake in the western contiguous United States. Spanning nearly 197 square miles, it’s 28 miles long and up to 15 miles wide, with over 185 miles of shoreline. Its size rivals some of the smaller Great Lakes in terms of surface area.

2. It Was Formed by Glacial Activity

Flathead Lake was formed at the end of the last Ice Age, carved by glaciers that once covered much of western Montana. The glaciers scoured out a deep basin, and when they melted around 12,000 years ago, they left behind the lake we see today. This glacial origin is also the reason for the lake’s exceptionally clear water.

3. The Water is Exceptionally Clear

Flathead Lake is renowned for its clarity. In some areas, you can see over 20 feet down into the water. This is due to its low nutrient content and the lack of urban runoff, thanks to minimal development along much of the shoreline. The lake’s clarity is often compared to Lake Tahoe, though Flathead remains one of the cleanest large lakes in the U.S.

4. It Has a Maximum Depth of Over 370 Feet

Though it may not appear as deep from the surface, Flathead Lake plunges to a maximum depth of about 370 feet (113 meters). The lake’s average depth is approximately 164 feet, making it a popular destination for deep-water fishing.

5. Named After the Flathead People

Flathead Lake is named after the Flathead Native American tribe, more properly known today as the Confederated Salish and Kootenai Tribes (CSKT). The southern half of the lake lies within the Flathead Indian Reservation, and the lake remains culturally significant to the tribes who have lived in this region for centuries.

6. Flathead Cherries are Famous Nationwide

Flathead Lake is famous for its sweet, dark cherries, known simply as Flathead cherries. Grown primarily on the eastern shores of the lake, these cherries benefit from the region’s mild microclimate. The Polson Cherry Festival, held each summer, celebrates this delicious harvest.

7. It’s a Hotspot for Fishing Enthusiasts

Anglers love Flathead Lake for its abundance of fish, including:

• Lake trout (mackinaw)
• Yellow perch
• Whitefish
• Northern pike
• Bull trout (protected, catch and release only)

Fishing tournaments such as Mack Days are held annually to manage non-native trout populations and encourage sustainable fishing.

8. Wild Horse Island is One of Its Most Unique Features

One of Flathead Lake’s most iconic attractions is Wild Horse Island, the largest island in the lake at 2,160 acres. The island is home to a herd of wild horses, bighorn sheep, deer, and many species of birds. It’s accessible only by boat and is a day-use state park ideal for hiking, photography, and wildlife viewing.

9. Multiple State Parks Line Its Shores

Flathead Lake has six Montana State Parks along its shores, offering public access for recreation and nature experiences:

• Big Arm State Park
• Finley Point State Park
• West Shore State Park
• Yellow Bay State Park
• Wayfarers State Park
• Wild Horse Island State Park

These parks offer campgrounds, boat ramps, beaches, and hiking trails, making Flathead Lake a perfect family-friendly destination.

10. The Lake Has Over a Dozen Islands

In addition to Wild Horse Island, Flathead Lake is dotted with over a dozen smaller islands, including:

• Cedar Island
• Bird Island
• Melita Island
• Bull Island

These islands offer habitats for wildlife and secluded spots for kayaking and boating.

11. The Flathead Monster: Local Legend Lives On

Like Loch Ness, Flathead Lake has its own legendary creature: the Flathead Lake Monster. Described as a large, serpent-like animal seen gliding through the water, the story dates back to Native American oral histories and early settler sightings. While there’s no scientific evidence, many locals and tourists still claim to have seen something mysterious in the depths.

12. It’s Surrounded by Scenic Towns

Flathead Lake is bordered by charming small towns that serve as gateways to outdoor fun:

◉ Polson (south shore) – Known for cherry orchards and museums

◉ Bigfork (northeast) – Famous for its art galleries and theater

◉ Lakeside (northwest) – A hub for water sports and dining

◉ Somers, Rollins, Woods Bay – Quieter communities with local charm

These towns offer everything from lakeside cabins to cafes and artisan shops.

13. A Gateway to Glacier National Park

Flathead Lake is just an hour south of Glacier National Park, making it a perfect addition to any northern Montana itinerary. Many visitors use Kalispell, Bigfork, or Polson as a base for exploring both the lake and the park in one trip.

14. Supports a Diverse Ecosystem

The lake supports a wide variety of species, including:

◉ Ospreys and bald eagles

◉ Waterfowl and songbirds

◉ Native and introduced fish

◉ Aquatic plants and macroinvertebrates

This ecosystem is protected through joint efforts by the State of Montana, CSKT, and environmental groups.

Flathead Lake Quick Facts

Location	Northwestern Montana, USA
Length	28 miles
Width	Up to 15 miles
Surface Area	197 square miles (510 km²)
Max Depth	370+ feet (113 meters)
Average Depth	164 feet
Water Clarity	Up to 20 feet visibility
Formation	Glacial origin from the last Ice Age
Notable Islands	Wild Horse Island, Melita Island, Bird Island
Known For	Clear water, Flathead cherries, Wild horses, Scenic beauty
Wildlife	Bald eagles, bighorn sheep, lake trout
Recreation	Boating, fishing, swimming, camping, kayaking
Cultural Significance	Home to Confederated Salish and Kootenai Tribes
State Parks	Big Arm, Finley Point, Yellow Bay, West Shore, Wayfarers
Nearby Attraction	Glacier National Park

Final Thoughts

Flathead Lake is much more than just a large body of water—it’s a vibrant hub of culture, wildlife, recreation, and history. Whether you're sailing across its clear blue waters, exploring Wild Horse Island, or simply enjoying a basket of Flathead cherries, the lake offers experiences as deep and unforgettable as the waters themselves.

Flathead Lake isn’t just known for one thing—it’s known for everything that makes Montana magical.