Trillium Lake is a lake situated 7.5 miles south-southwest of Mount Hood in the U.S. state of Oregon. It is formed by a dam at the headwaters of Mud Creek, tributary to the Salmon River. It was created by the state Department of Fish and Wildlife in 1960.The area which is now the lake was part of the Barlow Road, a component of the Oregon Trail. A log road across marshes allowed immigrants to pass to Summit Meadow, which was a toll station 1866—1870.