John Harris was born 21 June 1782 in Devonshire, England, the son of the local curate, also named John. At the age of 12 he ran away to sea and eventually joined the Royal Navy. He served in England and South America, and in March 1813 was sent to Kingston, ON, where he participated in the battle of Crysler's Farm during the War of 1812. After the war John remained in Ontario, where he joined a team that was surveying the Thousand Islands and Great Lakes. He met Amelia Ryerse in April of 1815 and married her on 28 June 1815.

John and Amelia settled first in Kingston, where Amelia assisted her husband with his surveying work. On 1 September 1817 John retired from the Navy and the Harrises moved to Port Ryerse, Amelia's birthplace. Their first son and first daughter died in childhood, but eventually they had ten more children who survived to adulthood. While in Port Ryerse John tried his hand at farming, as well as continuing his work as a surveyor. He was a great advocate of the advancement of scientific study in Canada and belonged to several academic societies. In 1832 he purchased land in London, ON, and proceeded to build a home there for his family. The Harris family moved to London and into Eldon House in 1834. Throughout the 1830s and 1840s John was active in both local and provincial politics, although he scaled back his activities in the later 1840s to focus on his community of London, and he served as Treasurer of London District for thirty years. He died on 25 August 1850, two days after his daughter Mary's wedding. He left his widow, Amelia, two married daughters, and eight children at home.