Emerald Lake was incorporated September 17, 1920, as a not for profit athletic, recreational and social facility. On August 25, 1926, the Anglo-California Trust Company of San Francisco deeded the property to the Emerald Lake Country Club for the sum of $10, with the following conditions: no building of any bar rooms, livery stables, undertaking establishments or blacksmith shops.

The lake began as a watering hole for cattle and for the stage coach horses that traveled between Pescadero and Redwood City in the late 19th century. The lake was later improved as a recreational facility for owners and renters of cabins in the area who came to escape the summer fog in San Francisco.

The water that fills the lake comes from several seasonal creeks. The lake itself is about 1.75 acres.