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 shows 902 residents, a 16.6% drop. History 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. Twin Peaks Sports, the I.O.O.F. Hall, and a number of other buildings in Challis are individually listed on the National Register of Historic Places, most as a result of an Idaho State Historical Society study of historical resources in the town. Highways - US 93 - to Salmon (north) and Mackay (south) - to Stanley (southwest) The Salmon River Scenic Byway uses both highways, from Stanley to Salmon. The junction with Highway 75 is south of Challis. 1983 earthquake On Friday, October 28, 1983, the Borah Peak earthquake occurred at 8:06 am MDT. The shock measured 6.9 on the moment magnitude scale and had a maximum Mercalli intensity of IX (Violent). 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 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. The two fatalities of the earthquake were in Challis; a store front fell on two children walking to school. 2020 earthquake On Tuesday, March 31, 2020 at 5:52 pm MST, an earthquake measuring 6.5 on the moment magnitude scale occurred, centered west of Challis. This was the second strongest earthquake in the state of Idaho ever recorded. Geography and climate Challis is located at (44.504260, -114.228279), at an elevation of above sea level. According to the United States Census Bureau, the city has a total area of , of which, is land and is water. Challis experiences a semi-arid climate (Köppen climate classification BSk) with cold winters, hot summers, and low precipitation throughout the year. Demographics 2010 census At the 2010 census there were 1,081 people, 502 households, and 277 families living in the city. The population density was . There were 598 housing units at an