Simoom Sound Post Office was opened 1 August 1912, located at SE 1/4 Lot 761 on the Wishart Peninsula facing Simoom Sound (50º50'10" - 126º30'05" as labelled on BC map 1EM, 1919). Some time before 28 June 1943 the post office was moved to the west side of Gilford Island (likely at the seaplane base 50º45'35" - 126º29'10" outside Echo Bay). Some time before February 1967 the post office was moved less than 1 mile south into the settlement at Echo Bay. January 1983 decision by Canada Post to close the post office was evidently reversed, and the Simoom Sound Post Office - located in the settlement of Echo Bay - remains open.
Source: BC place name cards, or correspondence to/from BC's Chief Geographer or BC Geographical Names Office