What county in the United States has the highest mean elevation?

Colorado is the state with the highest average elevation in the US and the 13 highest counties across the entire 50 states are in Colorado.
Lake County, in the centre of the state of Colorado, has the highest U.S. county mean elevation of 11,702 feet (3,567 m). Lake County is where Mount Elbert and Mount Massive, the two highest summits of the Rocky Mountains of the United States and Canada are located. Lake County also contains the highest U.S. county low point: the Arkansas River at the point Lake County meets Chaffee County with an elevation of 8,965 feet (2,733 m). The highest natural point in Lake County and indeed Colorado and the entire Rocky Mountains is the summit of Mount Elbert at 14,440 feet (4,400 meters) elevation
Lake County as of the 2020 census, had a population was 7,436. The county seat is Leadville which is the the only municipality in the county.

https://en.wikipedia.org/wiki/List_of_highest_counties_in_the_United_States