Riddle was
admitted to the bar in 1840 and began practice in
Geauga County, serving as
prosecuting attorney of that county from 1840 to 1846.
Early political career He served as member of the
Ohio House of Representatives from 1848 to 1850, and in 1848 called the first
Free Soil convention in Ohio. Riddle moved to
Cleveland, Ohio, in 1850. He was elected prosecuting attorney in 1856, and in 1859 he defended the
Oberlin slave rescuers.
Congress He served as a
Republican in the
Thirty-seventh Congress (March 4, 1861 – March 3, 1863), making speeches in favor of arming
slaves, the first on this subject that were delivered in Congress, and others on emancipation in the
District of Columbia and in vindication of
President Lincoln. He was not a candidate for renomination in 1862.
Later career After his term in Congress, Riddle served as
consul at
Matanzas, Cuba, in 1863 and 1864. He then returned to Washington, D.C., and again engaged in the practice of law. He was retained by the
State Department to aid in the prosecution of
John H. Surratt as one of the accomplices in the murder of President
Abraham Lincoln. He also served as law officer of the District of Columbia 1877–1889. He was in charge of the law department at
Howard University for several years after its establishment. ==Death and legacy==