Utah Gov. Gary Herbert confirmed late Tuesday that the fire burning near Park City had destroyed the homes in a subdivision about 10 miles northeast of town and burned at least 15 other structures such as vehicles, sheds and boats.
The blaze was among several others in the West, where fires have devoured dry grass and brush and burned to the edges of small communities in several states. In about a dozen Western states, crews were actively fighting fires where drought has dried out landscapes and contributed to extreme fire behavior.
Health officials, meanwhile, monitored air quality in areas that have been blanketed by smoke for days.
Shifting winds in Utah pushed the fire toward homes in the Lake Rockport Estates subdivision, said Steve Rutter, a fire management officer with the state, who spoke at a news conference late Tuesday.
"We have homes that are completely surrounded by black, vegetation completely gone. But we were able to preserve the homes," he said. "It looks really ugly right now. It's a big black spot but there are still a lot of people who will be able to go home when we open it back up."
About 250 homes were still "imminently threatened," he said.
Meanwhile, Herbert said the fire has grown to 4,000 acres, or more than 6 square miles. It is 5 percent contained. Two Black Hawk helicopters will be used to fight the fire Wednesday.
At times, the fire had moved at 50 feet to 80 feet per minute Tuesday when wind gusts reached up to 50 mph, Rutter said.
"All in all it could have been a lot worse," Rutter said.
More than 100 people were assigned to help fight the fire.
Evacuations were expected to remain in place until at least Wednesday evening.
Russ Moseley chose to stay in his home and fight back flames with a garden hose as it came within 150 feet, he told The Salt Lake Tribune. He said he could feel the heat radiating on his face and saw the fire swallow homes below his and blow up propane tanks.
"It's like being in Vietnam," Moseley said.
In west-central Utah's Skull Valley, more than 20 structures were threatened by the Patch Springs Fire that covered some 16 square miles. No evacuations had been ordered, though the fire remained about two miles from the town of Terra and homes on the Goshute Indian Reservation.
More than 200 firefighters were working to contain the largest blaze in Utah, which has jumped at least 6 miles across the border into Idaho. The lightning-caused State Fire has charred almost 33 square miles in steep and rugged terrain.
The fire was less than a mile from the Idaho town of Samaria on Tuesday, but a fire line south of the town has held, said fire information officer Rick Hartigan.
Nationwide, there were 35 large active fires burning Tuesday, according to the National Interagency Fire Center in Boise. All were in the West.
Even so, fewer than 3 million acres have been burned by U.S. wildfires this year, NIFC reported, well down from the 5.9 million acres that had burned by this time last year and 6.3 million acres that had burned through mid-August in 2011.
In Idaho, fire crews prepared to capitalize on favorable winds and lower temperatures to continue burnout operations around the small mountain community of Pine, where the Elk Complex remained the nation's No. 1 firefighting priority.
The lightning-caused fire had burned across more than 140 square miles, and fire officials were working to push the fire toward an area already torched by a massive fire last year, fire spokeswoman Ludie Bond said.
"Everything seems to be going smoothly," Bond said.
No buildings burned overnight Monday, though fire officials were still tallying structure losses in Fall Creek, a little community several miles south of Pine where flames rolled through on Saturday.
Pine and the neighboring mountain hamlet of Featherville, 8 miles from the flames, remained threatened.
Several new, lightning-caused fires also were reported on rural, federal lands in Idaho.
A wildfire near Glenwood Springs, Colo., prompted a small number of evacuations Tuesday, Garfield County Sheriff's Office spokesman Walter Stowe said. About 60 firefighters were battling the Red Canyon Fire with help from three single-engine air tankers and a heavy air tanker. The fire was reported Monday.
The dry conditions were prompting warnings from land managers across the West, including Wyoming, where rangers complained that too many abandoned campfires have not been property doused, despite the extreme fire danger.
So far this summer, 132 smoldering campfires have been discovered in Grand Teton National Park and the adjacent Bridger-Teton National Forest in northwest Wyoming, federal officials say.
"It is a lot because we're only midway through our fire season and to have that many negligent people is quite disconcerting," Bridger-Teton spokeswoman Mary Cernicek said.
Meanwhile, health district officials in northern Nevada were closely monitoring air quality concerns after a smoky haze from a wildfire in the Tahoe National Forest more than 60 miles away descended along the eastern Sierra front from Reno to Carson City.
McCombs reported from Salt Lake City. Associated Press writers John Miller in Boise, Idaho, Bob Moen in Cheyenne, Wyo., and Scott Sonner in Reno, Nev., contributed to this report.