When he retired from the office of mayor, in January, 1858, it was his intention to devote himself exclusively to business; but an unexpected concurrence of circumstances in the third congressional district led to his nomination and election to Congress by the Republicans, although the partisan opposition was largely in the majority. He continued to represent the district for eight consecutive years, and until he declined further service. He entered Congress just before the breaking out of the Civil War, and became a participant in the momentous legislative events of that period. He witnessed the secession of the Southern members from the two houses of Congress, and served through the whole period of the war and through one Congress after the war closed, embracing one half of President Buchanan's administration, the whole of Lincoln's, and one half of Johnson's. He served on the committees on the Pacific Railroad, on the District of Columbia, and on naval affairs, of which last important committee he was chairman during the two closing years of the war. In this last position he won much reputation by his mastery of information relating to naval affairs at home and abroad, and by his thorough devotion to the interests of the American Navy. Mr. Rice did not often partake in the general debates of Congress, but he had the confidence of its members to an unusual degree, and the measures which he presented were seldom successfully opposed. When occasion called, however, he distinguished himself as a debater of first-class ability, as was shown in his notable reply to the Honorable Henry Winter Davis, of Maryland, one of the most brilliant speakers in Congress, in defence of the navy, and especially of its administration during the war period. Notwithstanding his arduous labors as chairman of the naval committee, Mr. Rice's business habits and industry enabled him to attend faithfully to the general interests of his constituents, and to many details of public affairs which are often delegated to unofficial persons or are altogether neglected. All of his large correspondence was written by himself, and was promptly despatched. Governor Andrew used to say that whenever he needed information from Washington, and prompt action, he always wrote to the representative of the third district.