Bootleggers and Borders: The Paradox of Prohibition on a Canada-U.S. BorderlandBetween 1920 and 1933 the issue of prohibition proved to be the greatest challenge to Canada U. S. relations. When the United States adopted national prohibition in 1920 ironically, just as Canada was abandoning its own national and provincial experiments with prohibition U. S. tourists and dollars promptly headed north and Canadian liquor went south. Despite repeated efforts, Americans were unable to secure Canadian assistance in enforcing American