On Friday, October 28, 1983, the Borah Peak earthquake occurred at 8:06 am MDT, measured at 6.9 on the Richter Scale. The Challis-Mackay region experienced rather thorough damage, with 11 commercial buildings and 39 homes with major damage; while another 200 houses were damaged, minor to moderately. Mackay in particular, about 50 miles (80 km) southeast of Challis, experienced the most severe damage. Most of the city's large buildings on its Main Street were damaged, to some extent; eight of these buildings were deemed condemned and closed down. Most of these buildings were built from materials such as brick, concrete block, and stone, each varying. 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.