Pitkin County is a county in the U.S. state of Colorado. As of the 2020 census, the population was 17,358. The county seat and largest city is Aspen. The county is named for Colorado Governor Frederick Walker Pitkin. Pitkin County is included in the Glenwood Springs Micropolitan Statistical Area, which is also included in the Edwards-Glenwood Spri…Pitkin County is a county in the U.S. state of Colorado. As of the 2020 census, the population was 17,358. The county seat and largest city is Aspen. The county is named for Colorado Governor Frederick Walker Pitkin. Pitkin County is included in the Glenwood Springs Micropolitan Statistical Area, which is also included in the Edwards-Glenwood Springs Combined Statistical Area.