John S. Rock was what we might call an over achiever. He was an indefatigable abolitionist, a teacher, a doctor, a dentist, and a lawyer. Some say he coined the term "black is beautiful" but I am not sure anyone can really substantiate that. Either way - Rock was an accomplished fellow.
In terms of significant firsts during the Civil War era, in February 1865 Rock was the first black lawyer to be admitted to the bar of the Supreme Court.
Keep in mind the rapidity of change forged in the crucible of war. Only eight years earlier, in the Dred Scott case, the Court had denied that any black person could be a citizen of the United States.
I would wager that no white American could have predicted Rock's (or any black person's) meteoric rise in March 1857. The mere suggestion of it would have made people look at you funny, to say the least.
Rock died in Boston in December, 1866 of tuberculosis.