Definitions for "Foothills"
hilly land on the lower slopes of mountains
Foothills are geographically defined as gradual increases in hilly areas at the base of a mountain range. They are generally larger than hills, but not as tall as nearby mountains. Many neighborhoods and communities found in such a location are termed "the foothills".
The locations along the west of Denver are considered to be areas with elevations between 6,000 and 9,000 feet above Sea Level. The foothills include towns and cities such as Evergreen, Conifer, Georgetown, Idaho Springs, Estes Park, Nederland, Fairplay, etc. The southern suburbs of Denver have some areas that get up to about 6,000 feet in elevation and they also can have weather conditions similar to foothills locations due to the enhanced effect the terrain has on increasing local precipitation - but these areas are not technically considered to be "in the foothills".