Admitted to practice before the U.S. Supreme Court on Feb 1, 1865, via a motion by Senator Charles Sumner. Before becoming a lawyer in 1861, Rock was a teacher, one of the first Black dentists, and one of the first Black doctors after earning his M.D. in 1852. A fierce advocate against slavery and racial injustice, he recruited Black soldiers for the 54th Massachusetts Regiment during the Civil War.