Mackay then published a biography of John Paul Jones, the founder of the US Navy. While initially well received, and the subject of flattering reviews in the trade press, it was soon discovered that it was practically a copy of what those same reviews had marked as the last work on the man, that by Samuel Eliot Morison in 1942. That biography too had won the Pulitzer. Columbia University history professor David Armitage was quoted in the "New York Times" as saying that the book was "a spectacular and sustained act of plagiarism."