Aspen is a home rule municipality that is the county seat and the most populous municipality of Pitkin County, Colorado, United States. The city population was 7,004 at the 2020 United States Census. Aspen is in a remote area of the Rocky Mountains' Sawatch Range and Elk Mountains, along the Roaring Fork River at an elevation just below 8,000 feet above sea level on the Western Slope, 11 miles west of the Continental Divide.