Bancroft's first starring role was in Pony Express (1925), and the next year in Old Ironsides, but he went from historical pictures to the gritty world of the underground in such films as Underworld (1927) and Docks of New York (1928). He was nominated for the Academy Award for Best Actor in 1929 for Thunderbolt.
His family had been in America since 1632, and his father, Aaron Bancroft, was distinguished as a revolutionary soldier, clergyman and author. His son was educated at Phillips Academy, Exeter, at Harvard University, at Heidelberg, Göttingen and Berlin. At Göttingen he studied Plato with Heeren, New Testament Greek with Eichhorn and natural science with Blumenbach.
He concluded his years of preparation by a European tour, in the course of which he received kind attention from almost every distinguished man in the world of letters, science and art; among others, from Goethe, Humboldt, Schleiermacher, Hegel, Byron, Niebuhr, Bunsen, Savigny, Cousin, Constant and Manzoni. Bancroft’s father was a Unitarian, and he had devoted his son to the work of the ministry; but the young man's first experiments at preaching, shortly after his return from Europe in 1822, were unsatisfactory, the theological teaching of the time having substituted criticism and literature for faith. His first position was that of tutor in Harvard. Instinctively a humanist, he had little patience with the narrow curriculum of Harvard in his day and the rather pedantic spirit with which classical studies were there pursued. Moreover, he had brought from Europe a new manner, full of the affections of ardent youth, and this he wore without ease in a society highly satisfied with itself; the young knight-errant was therefore subjected to considerable ridicule.
A little volume of poetry, translations and original pieces, published in 1823 gave its author no fame. As time passed, and custom created familiarity, his style, personal and literary, was seen to be the outward symbol of a firm resolve to preserve a philosophic calm, and of an enormous underlying energy which spent itself in labour. He found the conversational atmosphere of Cambridge uncongenial, and with a friend he established the Round Hill school at Northampton, Massachusetts. This was the first serious effort made in the United States to elevate secondary education to the plane on which it belonged.
In 1844 he was the Democratic candidate for the governorship, but he was defeated. In 1845 he entered Polk's cabinet as Secretary of the Navy, serving until 1846, when for a month he was acting Secretary of War. During this short period in the cabinet he established the naval academy at Annapolis, gave the orders which led to the occupation of California, and sent Zachary Taylor into the debatable land between Texas and Mexico. He also continued his pleadings for the annexation of Texas, as extending “the area of freedom,” and though a Democrat, took high moral ground as to slavery; he likewise made himself the authority on the North-Western Boundary question.
In 1846 he was sent as minister to London, where he lived in constant companionship with Macaulay and Hallam. On his return in 1849 he withdrew from public life, residing in New York. In 1866 he was chosen by Congress to deliver the special eulogy on Lincoln; and in 1867 he was appointed minister to Berlin, where he remained until his resignation in 1874. Then he lived in Washington, DC and Newport, dying at Washington on the 17th of January 1891. His latest official achievements are considered the greatest. In the San Juan arbitration he displayed great versatility and skill, winning his case before the emperor with brilliant ease. The naturalization treaties which he negotiated successively with Prussia and the other north German states were the first international recognition of the right of expatriation, a principle since incorporated in the law of nations.
In spite of the exacting and severe routine of the Round Hill school, Bancroft contributed frequently to the North American Review and to Walsh's American Quarterly; he also made a translation of Heeren's work on The Politics of Ancient Greece. In 1834 appeared the first volume of the History of the United States.