Monticello Dam is a 304-foot high concrete arch dam in Napa County, California, United States, constructed between 1953 and 1957. The dam impounded Putah Creek to create Lake Berryessa 26-mile long reservoir.
The dam is 100 thick at the base, tapering to 12 at the crest. The total volume of construction materials is 326,000 cubic yards.
The dam is noted for its classic, uncontrolled morning-glory-type spillway. The diameter at the lip is 72 ft. Locally, the spillway is also known as the "Glory Hole".