The fire is burning in Southern California's Angeles National Forest, about 3.5 miles east of California Highway 39, and is only about 5 percent contained, the Los Angeles Times reported,
Forest officials were forced to evacuate campgrounds that bring in thousands of visitors every Labor Day weekend.
So far, no injuries have been reported, and officials said no structures are in immediate danger.
Investigators said it was believed the wildfire started Sunday after a car caught fire.
The evacuees left the popular recreation area Sunday afternoon, KTLA, Los Angeles, reported.
More than 200 firefighters were working in an area around Glendora, utilizing an array of air tankers, helicopters, brush engines, water engines and bulldozers.
The fire was moving northeast toward the Sheep Mountain Wilderness Area.