- Construction of Interstate 70 between Ward Road and West Colfax Avenue - U.S 40 (four miles) completed
- Construction of Interstate 70 between State Highway 26 and Lookout Mountain Exit - Mount Vernon Canyon (2.8 miles) and between Lookout Mountain Exit and Genesee Mountain (2.4 miles) completed
May 12, 1970
Denver is awarded the 1976 Winter Olympics. The organizing committee considers the Evergreen-Indian Hills area as a venue for the Nordic events. After public outcry over the costs and environmental impact, Denver officially withdraws on November 15, 1970, and the games are eventually awarded to Innsbruck, Austria.
Heritage Square opens on the old site of Magic Mountain.
June 10, 1971
Riot breaks out at Red Rocks Park before a Jethro Tull concert, resulting in the concert being cancelled and tear gas dropped on rioters from low-flying helicopters.
- Jefferson County voters approve a one-half percent sales tax for Open Space, inaugurating the county's award-winning Open Space Program
- Construction of Interstate 70 through remainder of Jefferson County completed (between Genesee Mountain and El Rancho Exit (two miles) and El Rancho Exit and Beaver Brook (four miles)
- NFL's Baltimore Colts hold training camp at Colorado School of Mines
- Lyle Fulkerson begins another Tiny Town restoration
- Colorado School of Mines celebrates its Centennial (100 years)
- The Astor House in Golden listed on the National Register of Historic Places
- First woman, Joanne K. Paterson, elected as a Jefferson County commissioner; she serves 1975 to 1979
- National Renewable Energy Laboratory established. Begins operating in 1977 as the Solar Energy Research Institute
- National Earthquake Information Center moves to Colorado School of Mines in Golden
- Casa Bonita restaurant opens in the JCRS Shopping Center on West Colfax Avenue in Lakewood. Awarded landmark status by the Lakewood Historical Society in 2015
- Regional Transportation District (RTD) formed
June 20, 1974
Two small planes collide over Crown Hill Cemetery. One plane falls to the ground in the cemetery and burns, killing four. The other plane belly-lands in Sloan's Lake; two men inside are able to get out before it sinks and are rescued by a boater.
July 22, 1974
Jefferson County Historical Commission established to guide the observances of the Centennial-Bicentennial year of 1976. The volunteer group now promotes the preservation and use of historical resources and sites around the county.
- United States Marine Corps memorial erected at U.S. 6 and Colfax - the only one outside of Washington, D.C.
- Morrison Historical Sites listed on the National Register
July 3 & 4, 1976
The Festival of the West, a Centennial-Bicentennial project of the Jefferson County Historical Commission, is held at the Jefferson County Fairgrounds.
August 1, 1976
Lakewood Heritage Center opens as Belmar Museum.
Coors Brewery workers strike.
Tiny Town closes and again falls into disrepair.
August 9, 1978
Major protest at Rocky Flats plant. 60 protesters, including Beatnik poet Allen Ginsberg, are arrested for trespassing.
November 4, 1978
Fire hits the Golden Transcript building at 1000 10th Street destroying its typesetting and layout equipment.
April 28 & 29, 1979
An estimated 15,000 people protest near Rocky Flats; 286 protesters are arrested for trespassing.
August 2, 1979
Heritage Square Alpine Slide opens and operates for 37 years before closing for good in 2015.