Sylvan Lake, known as the "crown jewel" of Custer State Park

Custer State Park

Custer State Park is a state park and wildlife reserve in the Black Hills of southwestern South Dakota, USA. The park is South Dakota's largest and first state park, named after Lt...

, is located in the Black Hills

Black Hills

The Black Hills are a small, isolated mountain range rising from the Great Plains of North America in western South Dakota and extending into Wyoming, USA. Set off from the main body of the Rocky Mountains, the region is something of a geological anomaly—accurately described as an "island of...

 of South Dakota

South Dakota

South Dakota is a state located in the Midwestern region of the United States. It is named after the Lakota and Dakota Sioux American Indian tribes. Once a part of Dakota Territory, South Dakota became a state on November 2, 1889. The state has an area of and an estimated population of just over...

. Created in 1881 when Theodore Reder built a dam across Sunday Gulch, it offers picnic areas, rock climbing, small rental boats, swimming, and hiking trails. It is also popular as a starting point for excursions to Harney Peak

Harney Peak

Harney Peak is the highest natural point in South Dakota. Harney Peak is located within the Black Elk Wilderness area, in southern Pennington County, within Black Hills National Forest...

 and The Needles

Needles (Black Hills)

The Needles of the Black Hills of South Dakota are a region of fantastically eroded granite pillars, towers, and spires. Popular with rock climbers and tourists alike, the Needles are accessed from the Needles Highway, which is a part of Sylvan Lake Road...

.

The lake was featured in the 2007 film National Treasure: Book of Secrets. The film made the lake appear to be located directly behind Mount Rushmore

Mount Rushmore

Mount Rushmore National Memorial is a sculpture carved into the granite face of Mount Rushmore near Keystone, South Dakota, in the United States...

when in fact it is five miles southwest of the monument.