Premise: Danville is an unincorporated community and census-designated place (CDP) in Ferry County, Washington, United States. Danville is located on Washington State Route 21 near the Canada–United States border, 31 mi north-northeast of Republic, the Ferry County seat. Danville has a post office with ZIP code 99121. The population at the 2010 census was 34.
Hypothesis: Danville zipcode is 99121.