The fire broke out on the edge of the Cleveland National Forest, about 10 miles east of Lakeside. It took 20 engine companies and 10 water-dropping aircraft about five hours to stop the fire's forward progress.
The fire is not threatening any homes, but it has prompted evacuations.
A pair of hikers and eight people in a cabin had to be rescued by a helicopter.
Also, some visitors to El Capitan Reservoir and El Monte Park had to be flown out.
"It's hard to explain how emotional it was, just not knowing how I'm going to get out," described Bryan Wettig, who was rescued from the fire.
According to officials, the fire has burned about 1,047 acres.
The Associated Press contributed to this report.