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.

Eagle County is a county located in the U.S. state of Colorado. As of the 2020 census, the population was 55,731. The county seat is the Town of Eagle and the most populous community is Edwards. The county is named for the Eagle River.