Johnson then finished his Ph.D. at Columbia University under James Harvey Robinson, with a dissertation entitled The Intendant as a Political Agent under Louis XIV (1899).
[1] While on the Yale history faculty, Johnson published an article supporting the constitutionality of the fugitive slave act of 1850.
[2] An interpretation of the article is that it was part of the movement to reconcile North and South, while supporting the southern side in arguments about the Constitution.
[3] Johnson's work as editor of the fifty-volume Chronicles of America series, which was acclaimed for its scholarship and high standards, led to his invitation from the American Council of Learned Societies to edit the proposed Dictionary of American Biography, which led Johnson to leave his position at Yale in 1926 and move to Washington, DC, to oversee work on the DAB.
[4] Walking home on the evening of January 18, 1931, Johnson tried to cross a street against traffic and was struck by an automobile, whose driver brought him to the hospital, where he was pronounced dead within an hour of the accident.