Business Loop I-70 - Golden and Denver

Business Loop I-70 crosses the Denver metropolitan area between the city of Golden to the west and Aurora to the east. According to the Denver Rocky Mountain News from June 19, 2000, Colfax Avenue is "the longest continuous commercial thoroughfare" in the United States. The business route follows all of Colfax Avenue, and it is cosigned with U.S. 40 throughout and with U.S. 287 east from Federal Boulevard. Business Loop I-70 is not acknowledged from Interstate 25 when it crosses paths with Colfax Avenue near Downtown.

The 27.47 mile route of Business 70 is one of the longest in the country. It is not inventoried independently by CDOT since it overlaps with state maintained sections of U.S. 40 and U.S. 287.

Colfax Avenue is named after Schyuler Colfax, an Indiana Congressman who passed through Colorado in 1865 and later became Vice President under Ulysses S. Grant. The street name supplanted 15th Avenue (M. Salek, personal communication).