Residents of two towns on the edge of a giant wildfire near Yellowstone National Park fled their homes, and firefighters Monday made a "last ditch" effort to stop the encroaching flames.

About 150 residents of Silver Gate and Cooke City, near Yellowstone's northeastern entrance, were told Sunday to evacuate.Only a few residents opted to stay.

"There's no real reason to leave," Cooke City's Wayne Johnson as firefighters moved past him. "I don't think the town's going to burn."

But officials were not as confident.

"If (the fire) jumps out of the line and explodes, it could burn up that canyon faster than they could drive out of there," said fire information officer Dave McMorran. "So we're spreading the word around tonight, `Don't sit around and wait, folks."

Crews lit a three-mile-long backfire Sunday night to burn up fuel in front of the 61,300-acre Storm Creek fire and protect the towns. The backfire was lit along U.S. 212 at Yellowstone's northeast entrance, a wooded canyon that fire officials fear may be the Storm Creek fire's next route.

By Monday this morning, the backfire had burned a half-mile away from the road. Fire information officer Bob McHugh said firefighters wanted two miles of "black line," fire line where all flammable material was burned, because the fire has been throwing burning embers up to a mile and a half.

The blaze was among fires that have blackened 910,000 acres of the greater Yellowstone area, including 611,000 acres within the park itself, or more than one-fourth of Yellowstone's 2.2 million total acreage. One blaze, the North Fork fire, was within three miles of Old Faithful geyser in Wyoming.

Elsewhere, swarms of fires in Southern California charred nearly 18,000 acres of brush and timber and damaged at least 26 buildings while low humidity, temperatures as high as 110 and Santa Ana winds harried firefighters and ignited new flames. One fire forced 150 people to evacuate from a mobile home park 15 miles northeast of San Diego.

In Idaho, a fire that spread from Yellowstone into the Island Park area of eastern Idaho during the weekend burned more than 14,500 acres, but light winds gave firefighters a reprieve. The state's largest fire, the Ladder Creek fire in central Idaho, grew to more than 21,000 acres.

"This group of fires is the largest complex of wildfires ever to burn in the written history of the continental U.S., excluding Alaska," Kaunert said. "This is a one-in-400 year event."