Horace E. Scudder: James Russell Lowell: A Biography. 2 vols. The standard biography.
Ferris Greenslet: James Russell Lowell: His Life and Work. The latest biography (1905) and very satisfactory.
Francis H. Underwood: James Russell Lowell: A Biographical Sketch and Lowell the Poet and the Man. Interesting recollections of a personal friend and editorial associate.
Edward Everett Hale: Lowell and His Friends.
Edward Everett Hale, Jr.: James Russell Lowell. (Beacon Biographies.)
Charles Eliot Norton: Letters of James Russell Lowell. 2 vols. Invaluable and delightful.
Edmund Clarence Stedman: Poets of America.
W.C. Brownell: James Russell Lowell. (Scribner's Magazine, February, 1907.) The most recent critical estimate.
George William Curtis: James Russell Lowell: An Address.
John Churton Collins. Studies in Poetry and Criticism, "Poetry and Poets of America." Excellent as an English estimate.