Mackay is a town in Custer County, Idaho, United States. The population was 439 at the 2020 census. The town is pronounced "Mackie" with the accent on the first syllable.

Challis is the largest city in Custer County, Idaho, United States. It is the county seat and its population was 1,081 at the 2010 census. The 2020 census showed 902 residents, a 16.6% drop. And as of