Firefighters went door-to-door deciding which homes they could save Monday as an explosive 68,000-acre wildfire nearby fed off heat, wind and timber.

All 17,000 residents of the Illinois Valley in southwestern Oregon were told to be ready to evacuate as the fire expanded through the Siskiyou National Forest. It was pushing south, on course to link up with another 20,000-acre blaze.

Illinois Valley Fire Chief Kyle Kirchner said he was urging everyone to leave before things get worse.

"As far as I'm concerned it's imminent," he said. "Everything we've attempted to do on this fire, the fire has reared up and kicked us in the face."

Though his home is six miles from the fire, Dennis Parker packed his house trailer and, along with his wife and two young children, was headed to his sister's house 40 miles away.

"I've got 20,000 gallons of propane by my back door, so I'm not going to hang around to see what happens." Parker said.

Meanwhile in Denver, officials closed Mesa Verde National Park on Monday and evacuated about 100 employees and an unknown number visitors as a fast-moving wildfire grew to more than 300 acres.

Four air tankers and two helicopters were on scene, fire information officer Larry Helmerick said. The park, 240 miles southwest of Denver, has an estimated 25,000 archaeological sites left by the Ancestral Pueblo Indians, a civilization that vanished more than 700 years ago.