From 1953 to 1989, the Rocky Flats Plant, a DOE nuclear weapon facility that was about 15 miles from Denver, produced fissile plutonium "pits" for nuclear warheads. A major fire at the facility in 1957, as well as leakage from nuclear waste stored at the site between 1958 and 1968, resulted in the contamination of some parts of Denver with plutonium-239, a harmful radioactive substance with a half-life of 24,200 years. A 1981 study linked the contamination to an increase in birth defects and cancer incidence in central Denver.

Known to locals as Blucifer, the 32 feet (9.8 m) tall sculpture is rumored to be cursed. Colored bright blue, with illuminated glowing red eyes, it is notable both for its striking appearance and for having killed its creator, Luis Jiménez, when a piece of the 9000 pound sculpture fell on his leg and severed an artery.

In a study looking at hail events in areas with a population of at least 50,000, Denver ranked 10th most prone to hail storms in the continental United States. In fact, Denver has received 3 of the top 10 costliest hailstorms in United States history, which occurred on July 11, 1990; July 20, 2009; and May 8, 2017.

In 1902, the police at Denver Union Station started enforcing a "no kissing" rule on platforms because it slowed down the trains.

McGaa, one of the first settlers of Denver, named several downtown streets, one of which was called Wewatta for his original Sioux wife. He named another street, Wazee, after his mistress. He also named McGaa Street after himself, but he was known as something of a drunk, and the street named in his honor was renamed after his death, lest it damage the town's reputation. Today, it is known as Market Street.

In 1993, Steve Ells opened the first Chipotle Mexican Grill in a former Dolly Madison Ice Cream store at 1644 East Evans Avenue, near the University of Denver campus, using an $85,000 loan from his father. Ells and his father calculated that the store would need to sell 107 burritos per day to be profitable. After one month, the original restaurant was selling over 1,000 burritos a day.

In 1867, Denver City became the acting territorial capital, and in 1881 was chosen as the permanent state capital in a statewide ballot. With its newfound importance, Denver City shortened its name to Denver.

In 1887, the precursor to the international charity United Way was formed in Denver by local religious leaders, who raised funds and coordinated various charities to help Denver's poor.

It's hard to think of any device in modern history that can provoke more feelings of intense rage, grief and sheer despair than the wheel boot, parking boot, or auto immobilizer. These are all names for what's commonly known as the Denver Boot--because that's where it was invented.

Extremes in temperature range from -29 °F (-34 °C) on January 9, 1875, up to 105 °F (41 °C) as recently as June 28, 2018.