Harper's Camp Post Office was opened 1 July 1897. Renamed Horsefly Post Office 1 July 1921.

Source: BC place name cards, or correspondence to/from BC's Chief Geographer or BC Geographical Names Office

"This name was derived from a mining camp established about 1884 or 1885 on the Horsefly River, just below the confluence of Moffat Creek. The lease was re-location of the original discovery claims of Peter Dunlevy and partners, staked in June 1859, being the first locations made on that River. Reports of the Minister of Mines for 1885, 1887, 1889 and 1890 show that Harper was in occupation of his lease then, but the report for 1891 shows that R.T. Ward, storekeeper at 150 Mile House, took it over in that year. In 1897 a post office was established with the name of Harper's Camp Post Office. In 1910 a school was opened with a similar designation and to the present day is so-named. The name of the Post Office was changed 21 July 1921 to Horsefly, which was formerly the name of a post office established 1 September 1895 about 6 miles further northward down the river where J.B. Hobson was operating mining claims. Upon cessation of work there the post office [had been] closed and the district was served by the Harper's Camp Post Office which however was changed in name to Horsefly on July 21, 1921 consequent upon a vote of the settlers in favour of the change."

Source: Laing, Frederick W; Geographical Naming Record, September 1938; unpublished manuscript held in the Provincial Archives