Much of the route overlaps other highways in Colorado, and, as a result, much of US 6 is unsigned.

US 6 is concurrent with Interstate 70 (I-70) for a significant portion of its length from the Utah state line to Denver.

Once it reaches I-25, US 6 travels north briefly, then follows I-76 for most of its length east of Denver.

The highest altitude along US 6 is 11,990 feet (3,650 m) at Loveland Pass, where it crosses the Continental Divide.

US 6 continues down Clear Creek and into Denver, where it turns into a freeway with six lanes.