William's Harbour is located on the south side of Granby Island, at the mouth of Alexis Bay, about 35 km east of Port Hope Simpson.
In the late 1970's the residents of William's Harbour believed they would have a better chance of obtaining electricity, a small school, and other services if they stayed at William's Harbour year-round. Soon after, the community of Rexon's harbour was abandoned with its residents residing in William's Harbour.

Until the late 1970's, William's Harbour was used only as a summer fishing station of nearby Rexon's Cove or Port Hope Simpson. The Harbour has believed to have been settled by the 1840's by the family of an Inuk named Samuel Kibenook (now spelled Kippenhuck), and was later joined by his son-in-law William Russell. Since that time the majority of residents are Russells and Larkhams.