where is challis id
Sponsored Topics. Challis is a city in Custer County, Idaho, United States. The population was 909 at the 2000 census. The city is the county seat of Custer County. Challis was founded in 1878 and named for A.P. Challis, who was a surveyor when the townsite was laid out. Challis post office was established in 1878.