Interstate 270 angles northwest from Interstate 70 by the Stapleton community in Denver through Commerce City and Interstate 25 by a commerce park area in southern Adams County. The freeway serves commuters west to Westminster and Boulder via connections with U.S. 36 and northeast Denver and Aurora beyond the east end with I-70.
On April 7, 2000, the Route Numbering subcommittee of AASHTO approved the extension of Interstate 270 from I-76 northwest to I-25. The freeway accommodates six lanes of traffic between I-25 and I-76, and just four southeast to I-70. Together with Interstate 76 west to Arvada and Wheat Ridge, I-270 provides a bypass of the oldest section of Interstate 70 through north Denver.
Preliminary numbering for the freeway connecting I-80S (now I-76) and Stapleton International Airport in Denver identified the loop as Interstate 425. The designation was changed to Interstate 270 by AASHO on February 26, 1959.1 Construction of the freeway began on December 12, 1965, with $2.7 million in projects including bridges over Dahlia Street, the Quebec Street overpass, and spans for I-270 over Interstate 70. The initial three miles opened to traffic northwest from I-70 to Vasquez Boulevard (U.S. 6-85). Further work on the two mile link between U.S. 6-85 and I-80S followed with completion on October 23, 1970.2
Construction on the extension west to U.S. 36 (Boulder-Denver Turnpike) and Interstate 25 started in April 1993. Coupled with work to extend Interstate 76 from I-25 to Pecos Street, Phase I work built an eastbound bridge for I-270 over I-25 and rebuilt the U.S. 36 east to I-25 north and southbound ramps. The $11.4 million phase was completed in June 1994. Subsequent construction started in June 1996 for westbound I-270 bridges over Washington Street and I-25, and a bridge connecting I-25 north with U.S. 36 west. Costing $12 million, that construction ran through May 1998.2
Costing $12 million, additional work from July 1997 to December 1998 built the I-270 westbound bridge over Clear Creek with associated work for U.S. 36 over Broadway and the I-25 southbound ramp to U.S. 36 west. The westbound extension of Interstate 270 was completed in February 2000 as part of an $19 million improvement project for I-25 and U.S. 36 from June 1998 to June 2001.2