Lake Clementine, Reservoir in the Sierra Nevada foothills, California, United States

Lake Clementine is a long, narrow reservoir on the North Fork American River, about 3.5 miles long and 300 feet wide in places, held back by the 155-foot North Fork Dam. The dam is a constant-angle arch dam with a 620-foot crest and six concrete piers; water pours over the crest in a broad white curtain beside a stepped spillway and a rocky outcrop. The reservoir has 280 surface acres and steep forested canyon walls.

Lake Clementine was formed in 1939 when the United States Army Corps of Engineers completed the 155-foot North Fork Dam, a constant-angle arch dam built to trap gold-mining debris washing downriver from hydraulic mining. The reservoir is owned by the Bureau of Reclamation and managed by California State Parks. Above the water, the limestone outcrop called Robbers' Roost served as a lookout for stagecoach bandits during the Gold Rush.

Lime Rock, a limestone outcrop visible from the lake and nearby trails, is known locally as Robber's Roost: during the Gold Rush it served as a lookout where bandits judged whether a stagecoach carried armed guards before signalling an attack. Some historians name Black Bart as leader of the gang. Upper Lake Clementine allows hand-and-pan gold panning.

Upper Lake Clementine is reached by a 1.5-mile switchback unpaved dirt road with its own entrance, separate from the lower lake, and is open May 1 to October 15 from sunrise to thirty minutes before sunset. The lower lake is boat-access only, with a boat-in campsite. Dogs are not allowed at the upper day-use beach.

The dam is a variable angle arch dam: its curvature changes along the horizontal profile, the crest runs 620 feet and the crown narrows from 22 feet at the base to 6.8 feet at the top. Because the river is designed to flow over the crest, the waterfall grows in winter and spring with rain and snowmelt.