The so-called Waldo Canyon fire sent a mushroom cloud of smoke nearly 6100m into the air over Colorado Springs near Pikes Peak, whose breathtaking vistas from the summit helped inspire the song "America the Beautiful".
Closer to the blaze, which has been fanned by hot winds blowing into the Southern Rockies from the prairies to the east, trees were visibly twisting from the heat of the flames.
Operators of a famous cog railway that carries tourists from around the world up the picturesque mountainside said the trains would remain shut down on Tuesday for a third straight day.
The highway that leads up to Pikes Peak has been closed since shortly after the fire erupted on Saturday, as has the popular Garden of the Gods, a picturesque park of tall, rocky spires and oddly balanced boulders.
Air tankers dropped fire retardant in the blaze's path to slow its advance, while firefighters on the ground battled to protect hundreds of homes along a highway at the mountain's edge including the upscale gated community of Cedar Heights. No homes were burned, although the fire consumed a wooden tent platform.
"We're feeling pretty good that's the only thing we've lost given this monster we are dealing with," said Rob Deyerberg, a fire information officer.
The closures around Pikes Peak, billed as the world's second-most visited mountain after Japan's Mount Fuji, have drawn attention to the fire's negative impact on the tourism industry just at the start of the peak summer travel season.
After three days, the blaze has scorched an estimated 4,500 acres (1,821 hectares), and fire crews managed to carve containment lines around just 5 percent of its perimeter. The cause was still under investigation.
Raging through dry timber about 130 km south of Denver, the Waldo Canyon fire had forced 11,000 people from their homes over the weekend, though residents from the town of Manitou Springs were allowed back on Sunday night.
One of them, Meg Duster, 27, stood watching the blaze from a safe distance at a fire command center. "I'm trying to remain optimistic, but it's so hard," she said, her voice quivering.
The US Air Force Academy in Colorado Springs was still about four miles (6.4 km) away from the leading edge of the blaze, though fire officials had earlier listed the complex as being in harm's way. A recreation area belonging to the academy was ordered evacuated due to its proximity to the fire, and all trails leading west of the school were closed, the base said.
The wildfire was one of about a dozen burning out of control around Colorado, including the monster-sized High Park Fire near Fort Collins, a university town north of Denver close to the Wyoming border.
"We're going to be continuing to have to deal with these fires for weeks to come," U.S. Forest Service Chief Tom Tidwell said. "We anticipate it's going to be a long fire season."
The High Park Fire - the state's second-largest blaze on record and its most destructive ever - has consumed 87,250 acres (35,308 hectares) in steep canyons since it was sparked by lightning two weeks ago. It is blamed for the death of a 62-year-old woman in her cabin and has destroyed 248 homes.
An estimated 4,300 people remain evacuated from their homes as that fire burns through grass, brush and Ponderosa pine.
In southwestern Colorado, the Weber Fire grew to 8,930 acres (3,615 ha) but firefighters held it back from the small town of Mancos, east of Mesa Verde National Park. Roughly 50 homes were evacuated, officials said.
Meanwhile, in neighboring Utah, a fast-growing 39,000-acre (15,780-ha) wildfire continued to rage largely out of control on Monday after burning an estimated 30 homes and killing 75 sheep between the rural communities of Fountain Green and Indianola.
Governor Gary Herbert, who toured the fire by helicopter on Monday, estimated the property losses so far at $7 million. No injuries have been reported, but Herbert said fire officials did use a helicopter to rescue some shepherds from the fire's path.
