June 12-20, 2000
The Hi-Meadow Fire burns 10,800 acres near Pine and Buffalo Creek, destroying 58 structures and threatening the historic Baehrden Lodge
September 11, 2001
Ken Caryl Ranch resident Jason M. Dahl is pilot of United Airlines Flight 93 when Al Qaeda terrorists hijack the plane to attack the United States. Passengers aboard the flight, believed to be targeting the White House or Capitol, fight back and succeed in thwarting the terrorists, crashing the plane near Shanksville, Pennsylvania. No survivors.
November 15, 2001
The city of four counties (Boulder, Adams, Weld, and Jefferson) officially becomes the City and County of Broomfield, withdrawing from Jefferson County
- Colorado Mills Shopping Center opens on West Colfax Avenue in Lakewood
- Jolly Rancher plant at 5060 Ward Road closes after 53 years
- Lariat Loop is designated Colorado's 24th Scenic and Historic Byway by the National Park Service
June 8-July 18, 2002
Hayman Fire, the largest wildfire in Colorado history at the time, burns southern Jefferson County and Douglas, Park and Teller counties, destroying 138,114 acres and 133 homes
March 18-19, 2003
Second largest snowstorm on record in Jefferson County dumps 50.5 inches of snow on Golden and other areas
- Laramie Building completed in Jefferson County Government Center campus at 3500 Illinois Street
- Lockheed Martin moves all rocket building to Alabama. Waterton Canyon location to be converted to satellite engineering under the name United Launch Alliance.
November 3, 2005
Major fire strikes Golden's historic Loveland block housing the Old Capitol Grill on Washington Avenue. Firefighters succeed in saving the building, confining the blaze to the second floor.
Clean-up of Rocky Flats declared complete
- Rocky Flats National Wildlife Refuge established on land formerly occupied by the Rocky Flats nuclear weapons production facility
- Foss General Store - a Golden landmark and destination - closes its doors after 94 years (1913 to 2007)
- Golden celebrates its Sesquicentennial - 150 years
- Lariat Loop becomes a National Scenic Byway, one of only 150 in the United States
- The Brook Forest Inn near Evergreen added to the National Register of Historic Places and the Colorado State Register of Historic Properties
- Historic Rockland Memorial Community Church and Cemetery added to the National Register of Historic Places