Remnants of the town of Mormon Island have been uncovered by the lake's receding waters, drawing people out to the lakebed in search of artifacts, The Sacramento Bee reported.
The lake's level is the lowest it's been since the winter of 1976-77, one of the worst droughts in state history, the California Department of Water Resources said.
In the 1800s, Mormon Island had a population of 2,500, but it dwindled to a few families by the 1940s.
The town founded by Mormon prospectors during the Mexican War once had four hotels, dry goods and other stores, and seven saloons.
Gold was discovered by members of the Mormon Battalion, who stayed in the area at the confluence of the north and south forks of the American River to continue prospecting.
The town was flooded after Folsom Dam was built in 1955.
So far, people have found rock-lined foundations, old glass, a doorknob and rusty nails. More items were expected to be exposed as the water continues receding.
Richard Preston of the California State Parks system says people are welcome to look at the remains, but that both state and federal laws prohibit the taking of artifacts.
"Our primary concern is the safety of the resource and to make sure people aren't carting off the history," he told the Bee.