Lake Eleanor, reservoir in Yosemite National Park

Lake Eleanor is a reservoir in Tuolumne County, California, surrounded by forested hills and rocky terrain. It has a calm water surface that mirrors the sky and trees along its banks, with trails leading around the lake and into the nearby woods.

The reservoir was created in 1918 by constructing an arched concrete dam as part of the Hetch Hetchy water system designed to supply San Francisco. This infrastructure was developed following debates about protecting the natural landscape, with conservationists like John Muir expressing concerns about the project.

The lake is named after Eleanor, daughter of Josiah Whitney, who led the California Geological Survey in the 1860s. On the south shore stands the Frog Creek Cabin, listed on the National Register of Historic Places since July 18, 2014. The reservoir is still owned and operated by the city of San Francisco.

Lake Eleanor sits in Yosemite's northwestern backcountry at 4,657 feet, reached by a remote road rather than a maintained highway, so check conditions before setting out. The reservoir is owned and operated by the city of San Francisco, and angling, hiking and camping are the activities it supports. The Frog Creek Cabin stands on the south shore, listed on the National Register of Historic Places since July 18, 2014.

Lake Eleanor Dam is the only multiple-arch dam ever built with elliptical rather than circular arches, a choice that cut the concrete needed at this remote site. Chief designer Michael O'Shaughnessy and hydraulic engineer R.P. McIntosh were responsible for the plan. The structure is 68 feet (21 m) high and 1,260 feet (380 m) long, and San Francisco still owns and operates it.