population 27, on Otter Creek, 7 mi. E of junction with Iditarod River, 59 mi. NE of Holy Cross, Kibuck-Kuskokwim Mts.
Mining camp reported in 1910 by A. G. Maddren U.S. Geological Survey (USGS), at which time Flat was the leading settlement on Otter Creek with a population of about 400. The post office has been in operation since 1912. Its population was 158 in 1920 and 124 in 1930.