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.[1] 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.[1]
His papers are at the Western Reserve Historical Society, Cleveland, Ohio. They include the unpublished manuscript Accounts of experiences in Cuba (1862–1864).[citation needed]
Works
Students and Lawyers, lectures (Washington, 1873)
Bart Ridgeley, a Story of Northern Ohio (Boston, 1873)
The Portrait, a Romance of Cuyahoga Valley (1874)
Alice Brand, a Tale of the Capitol (New York, 1875)
Life, Character, and Public Services of James A. Garfield (Cleveland, 1880)
The House of Ross (Boston, 1881)
Castle Gregory (Cleveland, 1882)
Hart and his Bear (Washington, 1883)
The Young Sugar Makers of the West Woods (Cleveland, 1885)[4][5]
The Hunter of the Chagrin (1882)
Mark Loan, a Tale of the Western Reserve (1883)
Old Newberry and the Pioneers (1884)
Speeches and Arguments (Washington, 1886)
Life of Benjamin F. Wade (Cleveland, 1886)
Recollections of War Times, 1860–1865
Ansel's Cave: A Story of Early Life in the Western Reserve (Cleveland, 1893)[6][7]