James Salmon Junior was a student of the Glasgow School of Art, who completed an architectural apprenticeship in the office of the acclaimed architect William Leiper. Early in his career, Salmon took the Grand Tour of Europe, and continued to travel widely during his lifetime, making visits to Spain, France, Germany, Switzerland, Norway, Belgium, Holland, Austria, Hungary, Romania, Turkey and Greece.

Following the death of his grandfather (James Salmon Senior), Salmon joined his father (William Forrest Salmon) in the family architectural practice, Salmon and Son. In 1903 the firm became Salmon Son & Gillespie, acknowledging the third significant partner of the firm, John Gaff Gillespie.