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St. Mary Lake is on the Eastern side of Glacier National Park. Going to the Sun road runs along its North shore. At 10 miles long and 300 feet deep it is the second largest lake in the park.
We boarded a ranger guided lake tour at the Rising Sun Dock, around the midpoint of the lake. I’d reserved it in advance with the Glacier Park Boat Company. The tour traveled from Rising Sun to the Baring Falls dock at the head of the lake in about 30 minutes, with Ranger Melissa narrating the whole way down.
As we traveled towards the Baring Falls dock at the head of the lake, we passed by Wild Goose Island, which we’d previously seen from a different perspective up on Going to the Sun Road.
As we approached the snow-covered peaks at the head of the lake, Melissa pointed out Sexton Glacier, visible on Mount Matahpi, just beyond Going to the Sun Mountain. Like most of the glaciers in the park, it is shrinking and has lost over 30% of its mass in the last 50 years.
We learned that the glaciers are the reason for St. Mary’s unique turquoise color. The slow movement of the ice grinds up the rock into a fine dust called glacial flour. The runoff carries the glacier flour into the lake where the particles remain suspended in the water, reflecting back the light.
Two Medicine and McDonald lakes are beautiful, but not the same vibrant hue as the East side lakes because there are no glaciers feeding into them. The NPS estimates that all the park’s glaciers will be gone by 2030 and then the Eastern lakes will lose their color.
At the dock, we disembarked and took a guided hike with Ranger Melissa. On the way back we passed another small island called Rainbow Island.
To see all of my Going to the Sun Posts, please click the following links:
- Rising Sun
- Wild Goose Island and Jackson Glacier Overlook
- Logan Pass
- Going To The Sun Road
- St. Mary Lake
- St. Mary Falls (Coming Soon)
Location: Going-to-the-Sun Road, East Glacier Park, MT 59434, USA
Designation: National Park
Date designation declared: 5/11/1910
Date of my visit: 6/24/2018

Love how you bring your posts to life with such great photography
Thanks so much!
I concur. Beautiful photos although the receding glaciers take away some of the joy of the moment.
Thanks! We are glad we went when we did!
I really like the shape of the mountains that surround St. Mary’s. As in so many locations, the loss of the glaciers is very concerning.
Thanks! Yes it is sad as certain species depend on the glacier ecosystem for survival.
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