Adopted by the Geographic Board of Canada 1 March 1904, as identified in British Admiralty Chart #3162, 1902 (Board files OBF 0176, C3521) - the northern portion of what was formerly Valdes Island.

Source: BC place name cards & correspondence, and/or research by BC Chief Geographer & Geographical Names Office staff.

The three islands now known as Quadra, Sonora and Maurelle Islands were once thought to be a single landmass, identified as "Valdes Island" on British Admiralty Chart #580, 1862. Okisollo Channel and Hole in the Wall (channel) were located and charted during subsequent surveys, and the label was adjusted to "Valdes Islands" (plural), until each island was given its own distinctive name by the Geographic Board.

Source: BC place name cards & correspondence, and/or research by BC Chief Geographer & Geographical Names Office staff.

Sonora was the schooner in which Spanish naval lieutenant Don Juan Francisco de la Bodega y Quadra sailed along the BC coast in 1775.

Source: BC place name cards & correspondence, and/or research by BC Chief Geographer & Geographical Names Office staff.

"While a lieutenant ("teniente de navio"), Quadra made two exploring voyages along this coast; the first one, in 1775, was in command of the schooner Sonora... and proceeded as far north as 58° latitude. On sailing southwards after passing what is now known as [Haida Gwaii] the Sonora kept too far off this coast to make any useful observations until southward of the strait of Juan de Fuca....."

Source: Walbran, John T; "British Columbia Coast Names, 1592-1906: Their Origin and History"; published for the Geographic Board of Canada, Ottawa, 1909 (republished for the Vancouver Public Library by J.J. Douglas Ltd, Vancouver, 1971)