Colorado's second-largest city, with a population of 430,000, also asked residents of 2,000 more homes to be ready to evacuate.
Gene Schwarz, 72, said he never fully unpacked after last year's fires. He and his neighbors wondered whether grassland to the north of them could be a barrier from the flames.
"It doesn't matter because a spark can fly over from anywhere," said Schwarz.
Black Forest, where the blaze began, offers a case study in the challenges of tamping down wildfires across the West, especially with growing populations, rising temperatures and a historic drought.
Developers describe Black Forest as the largest contiguous stretch of ponderosa pine in the United States — a thick, wide carpet of vegetation rolling down from the Rampart Range that thins out to the high grasslands of Colorado's eastern plains. Once home to rural towns and summer cabins, it is now dotted with million-dollar homes and gated communities — the result of the state's population boom over the past two decades.
Untold thousands of homes in Colorado's heavily populated Front Range are at risk for fires, said Gregory Simon, an assistant professor of geography who studies urban wildfires at the University of Colorado-Denver. Many are built on windy mountain roads or cul-de-sacs — appealing to homebuyers seeking privacy but often hampering efforts to stamp out fire. Residents are also attracted by the ability to hike from their backyards and have horses.
"Unfortunately, these environments give the appearance of being peaceful, tranquil and bucolic and natural. But they belie the reality that they are combustible, volatile and at times dangerous," Simon said.
Nigel Thompson was drawn to Black Forest by the rural feel, privacy, lack of crime and space to raise a family.
"A safe place for my kids to grow up, lots of room for them to run around," said Thompson, a computer programmer who moved to a house on a 60-acre lot in 1997.