[1] It is formed by Canyon Dam on the North Fork of the Feather River, as well as Benner and Last Chance Creeks, Hamilton Branch, and various natural springs.

[3][4] When the dam was built, Maidu families still living in the vicinity were displaced, while parts of the town of Prattville had to be moved to higher ground, leaving multiple structures flooded over.

The reservoir was named for the three daughters of Guy C. Earl, Vice President of Great Western Power: Alice, Martha and Eleanor.

PG&E uses it for hydroelectricity production, but the lake is also a popular recreation area, with fishing, boating, water skiing, swimming and camping available.

The California Office of Environmental Health Hazard Assessment has issued safe eating advice based on mercury for fish caught from Lake Almanor.

The wetlands at the north end also serve as breeding grounds for a variety of migratory waterfowl, most prominently Canada geese and various species of ducks including mallard, teal, and wigeon.