Denver's so-called "brick ordinance" requiring fire-resistant buildings was enacted in reaction to a large fire that wiped out a huge portion of the city's downtown business district in the 1800s.
The fire broke out sometime in the early morning hours of April 19, 1863, starting in the back of the Cherokee House saloon and hotel at 15th and Blake, according to the Denver Firefighters Museum.
By the time Denver residents woke up that morning, the fire had destroyed more than 70 buildings, with the estimated financial losses totaling somewhere between $200,000 and $350,000 (likely several million dollars today). There were no reports of deaths associated with the fire.
At the time of the fire, most of the buildings in Denver were built out of resin-rich pine, according to the Denver Firefighters Museum, making them especially susceptible to fire.
In response to the disaster, Denver enacted a new ordinance, referred to as the "brick ordinance," that required buildings to be constructed out of fire resistant materials like brick or stone.
Take a stroll through downtown or the city's older neighborhoods and you can see the evidence of this - buildings from the late 1800s and early 1900s are often built out of attractive reddish-brown stone or brick.
It isn't clear when the ordinance ended, but builders have been using wood frame construction in Denver for decades now and as of March 2017, there were more than 100 wood frame apartment buildings under construction or recently finished in the city.