The small concrete gravity dam built in 1913 is the only outlet from Lake Tahoe — it controls the level of America's second-deepest lake and the supply of the entire Truckee River system that feeds Reno and the Pyramid Lake basin downstream. The dam raises the natural lake level by just under two metres, which seems modest until you realise it stores enough water to supply Nevada agriculture for an entire dry year.
The gatehouse sits right next to Fanny Bridge; the dam itself is visible from the path along the river. It is a working piece of Western water infrastructure rather than a tourist sight, but understanding it explains why the lake looks the way it does.