The lake originally was a long narrow broadening of the Skokomish River formed in a glacial trough and dammed by a terminal moraine from the Vashon Glaciation during the most recent ice age.

As a popular retreat for hiking, fishing, boating and kayaking, Lake Cushman's shoreline is dotted with resorts and rental cabins.

The lake is notable for its beautiful crystal clear blue water and the huge round rocks surrounding it, as well as thick stands of hemlock, fir and cedar trees.

[1] In 1889, the Antlers Hotel was built on Lake Cushman by a pair of East Coast businessmen on the property of Russell Homan.

[6] In August 2020, the U.S. Forest Service temporarily closed all public roads leading to Lake Cushman due to concerns of overcrowding amid the COVID-19 pandemic.

A 6-mile (9.7 km) weekend traffic jam on the lake's primary two-lane, unpaved road had caused concerns about access for emergency vehicles, including an incident where one man died of drowning.

[citation needed] Swimming, boating, kayaking and cliff jumping are also among the most popular activities for Lake Cushman visitors.