Aspen is the home rule municipality that is the county seat and the most populous municipality of Pitkin County, Colorado, United States. Its population was 6,658 at the 2010 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.Founded as a mining camp during the Colorado Silver Boom and later named "Aspen" because of the abundance of aspen trees in the area, the city boomed during the 1880s, its first decade of existence. The boom ended when the Panic of 1893 led to a collapse in the silver market, and the city began a half-century known as "the quiet years" during which its population steadily declined, reaching a nadir of fewer than a thousand by 1930.