Charles Callan Tansill (1890–1964) was an American historian and the author of fourteen history books.

[2] In 1927, he edited Documents Illustrative of the Formation of the Union of the American States, published by the Library of Congress.

"[4] However, in a review for The Yale Law Journal, Frederick L. Schuman, a Professor of Political Science at Williams College suggested Tansill failed to be objective in his isolationist stance.

He argued, "In chapter headings, text, selection of facts, and emphasis, Dr Tansill reveals his pro-German and anti-British bias and his conviction that German victory was preferable to American intervention.

"[5] In the 1930s, Tansill was a staunch isolationist, arguing that the United States should not participate in World War II.

"[1] These assertions were confirmed as facts by President Herbert Hoover based on his discussions with the American ambassador to the United Kingdom at the time, Joseph Kennedy Sr, and the diaries of the Under-Secretary of the Navy, James Forrestal in his book “Freedom Betrayed.”[7] In an article that he published in American Opinion, the journal of the John Birch Society, in 1963, a year before his death, Tansill suggested it would have made sense to impeach President John F. Kennedy after the latter suggested to the United Nations that the United States should disarm.