He was the editor of a centennial history of Canada called Canada: Unity and Diversity and of a series of social studies volumes - writing one of them along the way (The Fishermen of Lunenburg).
From 1970 to 1980 Marsh was the editor of the Carleton Library Series, a series of scholarly works on Canadian history and social science that made a significant contribution to the growth of Canadian studies in universities.
In 10 years he edited 60 volumes in the series while co-authoring his first textbook on Canadian history, New Beginnings.
After 33 years as the founding editor of The Canadian Encyclopedia, James Marsh retired on March 31, 2013.
He was described as a 'Canadian who changed the world' by The Globe and Mail newspaper.