The main building of an historic, backcountry chalet in Glacier National Park in northern Montana burned in a wildfire Thursday evening.

The two-story Sperry Chalet was lost despite efforts by firefighters to protect it and save it, fire officials said.

"The firefighters, supported by 3 helicopters, made a valiant stand to save the structure but were unsuccessful in saving the main Sperry Chalet," according to a statement posted on a federal fire website.

No one was hurt, and firefighters were working to save other buildings of the chalet. The chalet had been closed since Aug. 15 because of the fire.

The Sperry Chalet was built in 1913. It has been listed on the National Register of Historic Places since 1977.

Elsewhere in Montana, a wind-driven wildfire ripped through parched forest and grasslands in southeastern Montana, threatening 35 homes and structures and forcing the evacuation of an undetermined number of residents scattered in the area, officials said Thursday.

The fire that started in the Custer National Forest about 35 miles (56 kilometers) northwest of Broadus on Wednesday burned at least 47 square miles (121 square kilometers) in a single day.

Authorities issued evacuation orders for the ranches and houses that dot the landscape in the direction the fire is heading. It is unclear how many people are affected by the order, but fire officials say 35 homes and other structures are threatened.

"It's growing exponentially," said U.S. Bureau of Land Management spokesman Mark Jacobson. "A lot of those people are sparse and spread out."

It's one of 45 fires that ignited Wednesday in Montana, where more than 90 percent of the land is in moderate to exceptional drought. Many of the new ignitions were caused by lightning strikes from a passing thunderstorm that carried little rain.

Unrelenting wind gusts caused the fire to spread too fast for crews to establish containment lines initially, and crews focused on protecting the buildings in the fire's path.

Wind gusts and low humidity hampered firefighting efforts again on Thursday.

A 20-person crew and equipment arrived Thursday to help the 70 people working on the fire, but firefighting resources are stretched and are being diverted to catch new fires before they spread, Jacobson said.

"We have a lot of other fires that are popping up all around this fire," he said. "The situation is rapidly evolving. They're doing their best with what they have."

Montana officials plan to nearly triple the number of National Guard troops deployed to fight fires by the end of the weekend. Those 350 soldiers will work on fire lines, firefighting aircraft and provide security in fire zones, Adjutant Gen. Matthew Quinn said.

With personnel and equipment scarce across the nation, those troops could free up other firefighters to focus on keeping small blazes from turning into large ones, Montana Department of Natural Resources and Conservation Director John Tubbs said.

"We need people on the ground fighting fire and we've asked the Montana Guard to step up," he said.

So far this year, more than 1,500 fires have burned 937 square miles (2,426 square kilometers) in Montana as the state suffers a drought that intensifies each week. The fires have already drained the state's firefighting reserve fund and an emergency fund, and there is no end in sight for the hot, dry weather that the fires are feeding on.

In northern Montana, a wildfire burning between Havre and the Rocky Boy's Indian Reservation has destroyed five cabins, five other structures and is threatening another 130 buildings, Hill County officials said.

Residents in the area have been notified that they may have to evacuate if the 17-square-mile (44-square-kilometer) spreads. It was uncontained as of Thursday afternoon.

In western Montana, fire crews continued to hold the line against a blaze that was threatening Seeley Lake. More than 1,000 homes and businesses in the town are under evacuation orders.