1942 had 2 winners of the Governor-General's Award for Literary Merit in nonfiction. Edgar D. McInnis also won the award for The Unguarded Frontier : A History of American-Canadian Relations. The title really says it all with this one. McInnis describes the history of the U.S./Canada border. In particular, he does a nice job of illustrating the complex dynamic between Britain, Canada, and the United States. In this respect, he traces the development of Canada from colony to independent state (within the framework of the Commonwealth) very effectively. Additionally, McInnis delves into a variety of specific border disputes. He conveys how the border was often determined well before any exploration, which often resulted in a final, haphazard boundary based more on negotiations than geography. It is in these sections, that I find his writing and expertise the strongest and his voice at its most unique. In fact, I found myself wanting more details as to the particulars of each boundary dispute.
Overall, I recommend The Unguarded Frontier as a nice survey of the history of Canada/U.S. relations.