Giant 2,000-year-old sequoias were treated with fire retardant to protect them against flames advancing today through the majestic forest that photographer Ansel Adams captured on film.
In Oregon, 1,200 Army soldiers were being sent to take up firefighting positions. Fires also burned in Alaska, Washington, Idaho and Utah.
Drought and the threat of more lightning in California worried fire officials after more than 200,000 acres burned statewide in the last week.
"More lightning means more fires," said Forestry Department spokesman Chris Parker. "What we're seeing is the culmination of four years' drought."
Yosemite was declared off-limits to tourists Friday. By Sunday more than 2,200 firefighters were battling two fires in the park that have burned 17,000 acres. The flames were about 10 miles from landmarks like El Capitan, Half Dome and Yosemite Falls, and within two miles of a stand of giant sequoias.
Workers tried to protect the trees by clearing debris and undergrowth from around their trunks and applying a chemical fire retardant.
Seventy-five people fled a park settlement Sunday to escape one of the fires.
Fires have burned 127 structures since last week in California ranging from outbuildings to homes. Sixty-six were in Foresta, near Yosemite. The park, which usually gets 25,000 weekend visitors, was empty of tourists.
"There's a degree of peacefulness, if you are not caught up in the frantic business of firefighting," said Jeff Nicholas, curator of Yosemite's Ansel Adams photo gallery.
More than $10 million in property has been destroyed by the fires, Yosemite fire officials said. The cost of fighting the fire had passed $1.5 million Sunday evening.
The park's chief naturalist, Len McKenzie, called the fires catastrophic and blamed past park management for the size and intensity of the blazes. By suppressing all wildfires in the forest, he said, a huge buildup of dead wood, dry grass and other fuel developed.
Thunderstorms like those that brought 24,000 recorded lightning strikes last week to California were expected to return by Tuesday.