December 13, 1921
Satanic Coal Mine disaster near Morrison claims lives of six men and injures one as mine fills with deadly firedamp gas.
Chief's Inn, or Ho Cha Nee Stea built as a local tea room and soda fountain for sightseers and prospective land buyers in Indian Hills.
April 14, 1922
The first public gathering of the Ku Klux Klan in Jefferson County on the present site of Heritage Square, complete with blazing torches. The targets of KKK intimidation in Jefferson County are Catholics, Jews, and blacks.
September 27, 1923
Ku Klux Klan erects and burns a large wooden cross on top of South Table Mountain on Castle Rock above Golden. It becomes major regional meeting place of the Klan.
- First Homecoming celebration for the Colorado School of Mines is held
- Octagon House in Indian Hills is built. Landmarked in 2004
- Washington Avenue in Golden is paved for the first time and lined with ornamental streetlights
- The beginning of Tiny Town's heyday. It has 125 buildings including a genuine pueblo structure with Indians from a New Mexico reservation, and hosts 20,000 visitors per year.
- NaTeSo Pueblo built in Indian Hills as a promotional real estate project by George Olinger. Made of adobe bricks handmade and laid by members of the Navajo, Tesuque and San Ildefonso nations brought up from New Mexico by Olinger.
- Mars Candy Company names Coors its Number 1 malted milk supplier (during prohibition)
May 2, 1925
Moonshine still explosion causes forest fire in Coal Creek Canyon.
- Temple Hoyne Buell designs the third Fruitdale School at 10801 W 44th Avenue in Wheat Ridge. Building design reuses portions of the foundation of the second Fruitdale School which burned in 1926. Added to the National Register of Historic Places in 2013.
- Vera West becomes the first woman editor of a Golden newspaper (wife of George West's son Harley)
August 7, 1927
Dance hall on top of Golden's Castle Rock burns down, believed caused by arsonists.
April 5, 1928
Sheriff Walter Johnson institutes fingerprinting and photographing each prisoner for identification purposes in the Jefferson County Jail.
Turkey Creek flood damages Tiny Town.
June 5, 1929
Adolph Coors dies in Virginia Beach, Virginia after falling from a sixth-floor balcony at the Cavalier Hotel.