The northern part of the range, north of Mount Rainier, is known as the North Cascades in the United States but is formally named the Cascade Mountains north of the CanadaâUnited States border, reaching to the northern extremity of the Cascades at Lytton Mountain.
The perimeter of Washington Park in Denver, CO is about 2.60 miles.
It is a totally reasonable plan. Vail is about 100 miles from Denver--1-70 all the way. It should take about 2 hours if you arrive at a non-rush hour time of day. Now if there's a snow storm that day, it will take longer, obviously.