The Rattlesnake Bar area between El Dorado and Placer Counties was once a famous crossing utilizing the old Rattlesnake Bar Bridge, seen towards the top of the photograph. That bridge was doomed, as Folsom Dam would be constructed downstream starting in 1952, with the reservoir beginning to fill in February 1955. Before that, a truck carrying fertilizer exceeding the 8-ton limit collapsed the bridge, and with the dam in the works, the bridge was never repaired.
The photograph above shows some kids playing in the tranquil waters of the north fork of the American River at a well-known swimming hole below the bridge. We are looking from the Placer County side to the El Dorado County side in the historic photograph. Before the upstream dams, the river waters would drop quite low, and become quite warm during the summertime, making for some sweet swimming holes.
This location is now under the waters of Folsom Lake most of the year. During the late summer or droughts, the water drops low enough that the old concrete supports for the bridge reappear.