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.
Belle Creek, Black Creek, Bonanza Creek, Boulder Creek, Butte Creek, Caribou Creek, Chicken Creek, Fairbanks Creek, First Chance Creek, Flat Creek, Franklin Creek, Granite Creek, Happy Creek, Julie Creek, Little Caribou Creek, Little Creek, Little Eldorado Creek, Martin Creek, Murray Creek, Prince Creek, Slate Creek, Tango Creek, Widgeon Creek, Willow Creek, Zimmerman Creek,
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