Homer Ransford Watson was born on 14 January 1855, in Doon, Ontario, the second of Ransford and Susan Mohr Watson's five children. A small village founded in the 1830s at the junction of Schneider's Creek and the Grand River, Doon's earliest documented population was 150 in the 1871 census. Watson descended from German Mennonite settlers who arrived in Ontario in the early 19th century. His father, a mill and factory owner, died in 1861 when Watson was six years old. Following Ransford's death, the family's only source of income was Susan's work as a seamstress. Ransford left behind a library of books that Watson studied from and influenced his early drawings. A gift of a set of paints from an aunt made him decide to become an artist. He sought the advice of Thomas Mower Martin in Toronto, and moved there in 1874. He copied works at the Toronto Normal School and was mainly self-taught, but met other artists in Toronto (e.g., Lucius O'Brien) while working part-time at the Notman-Fraser photography studio.