It is formed by a dam at the headwaters of Mud Creek, tributary to the Salmon River.
A log road across marshes allowed immigrants to pass to Summit Meadow, which was a toll station 1866—1870.
Adjacent Trillium Lake Campground is administered by the Zigzag Ranger District of the Mount Hood National Forest.
The large campground features a seasonal boat ramp and wheelchair-accessible floating dock.
[6] The lake is a very popular Nordic skiing destination from a trailhead across U.S. Route 26 from Snow Bunny.