More formally known as Earthquake Lake. Quake Lake was formed by the biggest recorded earthquake in Montana history: a 1959 rumbler that registered 7.5 on the Richter Scale and triggered an 80-million-ton landslide into the Madison River that killed 28 campers and dammed the Madison, creating Quake Lake just downstream of the Hebgen Lake dam.
Quake Lake, its shallows studded with drowned standing trees, reaches depths of 190 feet and measures 6 miles long, mostly within Gallatin National Forest, much of its north shore accessible via US 287. The lake is considered good fishing, and stocked with cutthroats and brown trout.
There's a campground at the lake's eastern end at coordinates 44.861345,-111.372914. A nearby boat ramp is at 44.854591,-111.387613.