He is best known for his History of the People of the United States from the Revolution to the Civil War (1883 sqq.), a valuable supplement to the more purely political writings of James Schouler, Von Holst and Henry Adams. He began working on it in 1873, having collected material since 1870. His A School History of the United States (1897) was an extremely popular textbook for many years. Besides these books and numerous magazine articles, he wrote Life of Benjamin Franklin in the "Men of Letters" series (Boston, 1887).