For the majority of the Civil War, Canadians were divided in their loyalties to the Union and to the South. However, in 1864, after years of sending agents and conspirators into Canada, the South became bolder in their affairs north of the border. These efforts culminated into two attacks, planned and executed from Canada by the South: The seizing of the Philo Parsons on Lake Erie on September 19, 1864; and the raid on St. Albans, Vermont, a month later, on October 19, 1864. These two attacks forced Canada and Great Britain to reassess their neutrality and, under pressure from the Union, Canada had to adopt more stringent neutrality laws. Canada also lost its nearly unfettered access to the much-needed American market when the Union cancelled the Reciprocity Treaty in early 1865.
Connolly, Michael R. D.
""Good Neighbourhood": Canada and the United States' Contentious Relationship During the Civil War,"
The Gettysburg College Journal of the Civil War Era: Vol. 11, Article 5.
Available at: https://cupola.gettysburg.edu/gcjcwe/vol11/iss1/5