Metolius Springs form the headwaters of the Metolius River in central Oregon, just north of Black Butte near Camp Sherman. The river begins at full strength there and flows 29 miles through the Deschutes National Forest to Lake Billy Chinook, making it one of the largest spring-fed rivers in the United States. Geologists believe the springs originated about 1.5 million years ago after Black Butte erupted and blocked a north-flowing river, forcing water to seep through porous rock and emerge on the north side. Two spring groups supply the source, releasing about 50,000 gallons per minute. Sam Johnson later helped preserve the area and donated the viewpoint to the United States Forest Service in 1965.