Firefighters were waiting until sunrise to count the exact number of houses that have burned, said Brett Haberstick of the Sunshine Fire Protection District.
The blaze broke out Monday morning in Four Mile Canyon northwest of Boulder and rapidly spread across 5 1/2 square miles or 3,500 acres. Erratic 45-mph gusts sometimes sent the fire in two directions at once.
Crews managed to save the historic town of Gold Hill, including an old West grocery store and structures once used for stagecoach stops. But firefighters in the area had to relocate their engines and equipment several times to avoid the flames.
"The fire moved too quickly and was much more active than anticipated," Haberstick said.
Despite the fire's destructive advance, no injuries have been reported, although some residents told of narrow escapes.
"I just drove through a wall of flames," Tom Neur told KDVR-TV. "The bumper is melted off in the front of the van."
Neur's wife, Anna, left earlier, and the couple reunited at temporary shelter. They said their house was destroyed.
"I don't care about the house," Anna Neur told her husband. "I'm just glad you're OK."
Fire managers said 1,000 homes had to be evacuated from the canyon and surrounding areas. Four belonging to firefighters were destroyed. Those firefighters were allowed to leave to attend to their families and personal affairs, said Laura McConnell, a spokeswoman for the fire management team.
More than 100 firefighters were on the scene on Monday, and the winds quieted enough by late afternoon to allow three tankers to drop more than 40,000 gallons of fire retardant along the leading edge of the fire.
The winds pushed the fire through three canyons where pine trees have been left prone to fire by disease, drought and beetles that burrow under the bark of pine trees, fire managers said. Such beetles have killed more than 3.5 million acres of trees in Colorado and southeastern Wyoming.
"We haven't had any rain there for almost a month. Maybe more than a month," said Craig Douglas, who lives north of the fire and received a knock on the door from a sheriff's deputy at about 8 p.m. on Monday. "The humidity the last couple of days has been in the single digits, so it was a fire waiting to happen."
The cause of the fire was unknown, and officials said it was too early to say how much, if any, of it was contained.
"It's very rocky, hilly, mountainous terrain," said Boulder County sheriff's Cmdr. Rick Brough.
Video from KUSA-TV showed at least one home engulfed in flames.
"There is ash falling from the sky," David Jones told The Denver Post from his home in Gold Hill, where about 250 people live. "We're getting out of here."
Officials said one fire vehicle was destroyed by the blaze.
Some ground crews remained at the fire through the night. At least four more aerial tankers were requested to join the fight Tuesday morning.
More than a half-dozen dirt roads that thread the narrow canyons were closed.
A billowing, white plume of heavy smoke was visible for miles before sunset. County health officials advised residents to stay indoors if the smoky air became irritating.
The Boulder County alert system malfunctioned for about two hours Monday afternoon, leaving authorities unable to send automatic calls telling residents to evacuate. Officials said it began working again later.
The Red Cross set up an overnight evacuation center at the Coors Events Center on the University of Colorado campus in Boulder. Douglas and about a dozen others were there early Tuesday.