Monticello Dam

Monticello Dam is an arch dam and hydroelectric power station in Napa County, California. The concrete structure crosses Putah Creek valley and forms Lake Berryessa, which sits among wooded slopes of the Vaca Mountains.

Construction took place between 1953 and 1957 as part of an irrigation and power project for the region's growing communities. Before work began, residents of Berryessa Valley left their homes and hundreds of graves were relocated.

The reservoir serves as a primary drinking water source for area residents while feeding extensive irrigation systems downstream. The name Berryessa recalls an early settler family whose ranch once stood along the banks of Putah Creek.

The dam itself is not open to the public for safety reasons, but viewpoints along the lakeshore offer a good view of the structure. Visitor centers around the lake provide information about how the dam works and its background.

A funnel-shaped spillway measuring 22 meters (72 feet) across channels excess water through an underground tunnel back into Putah Creek. This morning-glory spillway is one of the largest of its type in the world.

Location: Napa County

Elevation above the sea: 138.5 m

GPS coordinates: 38.51345,-122.10466

Latest update: December 5, 2025 16:33