Choking wildfire smoke completely engulfed big sections of Yellowstone National Park Friday and was as much a problem as the flames rampaging over 385,000 acres of its dry forests, forcing the closure of miles of roads.

Thick gray and black smoke poured from seven big fires roaring through the interior and at all four corners of the scenic 2.2-million acre wilderness sanctuary, the first to be designated a national park 116 years ago.Visibility in the worst areas was near zero. Tourists heading to the popular park - home to 3,000 geysers and hot springs, including famed Old Faithful, and large populations of elk, bison and grizzly bears - were warned to take precautions.

"Smoke conditions vary from very heavy to moderate," park spokeswoman Joan Anzelmo said. "Smoke is especially heavy in the mornings and visibility is poor. Anyone with respiratory problems should consult with their personal physician before visiting Yellowstone at this time."

But more than 10,000 tourists - some even drawn by the spectacle of the walls of flames - remained in the park, which is bounded by Wyoming, Idaho and Montana.

"Some days the fires are an attraction to the public, especially the smoke columns," Anzelmo said.

Hundreds of miles to the west, about 10,000 acres of forest and range land were ablaze across southern Oregon. More than 1,500 firefighters battled 11 major fires burning out of control that forced farm residents and school children at a Bible camp to flee. More evacuations at a Grants Pass subdivision were threatened.

Montana, suffering its worst drought in history, contended with 130,000 acres of wildfires. Other fires burned in Wyoming, Idaho, Washington, California and Utah.

National Weather Service satellite photos showed smoke from Yellowstone Park's worst fires in history drifting over virtually all of Wyoming and through Colorado, Nebraska, South Dakota, Kansas and as far as Kansas City, Mo.

The pall of smoke 8,000 to 10,000 feet over southeast Wyoming turned the sun red again.

Much of Yellowstone's road system has been closed by the fires, which are expected to burn until the arrival of autumn rains or snows despite a summer-long firefighting battle that has surpassed $30 million in cost.

There were 3,500 firefighters, some from as far away as Hawaii, and 1,200 Army troops on the lines.

"The dependable travel routes are in the north entrance and the northeast entrance," Anzelmo said.

The west entrance to Old Faithful was closed while firefighters cleared dead trees dropped across the road by the North Fork Fire. Old Faithful, reachable by another route, was still open to tourists, however, as it has been throughout the summer, Anzelmo said.