One of Nast's most passionate causes, freeing the slaves, was the subject of many of his wartime illustrations - most notably "Emancipation," a two-page woodcut engraving that appeared in Harper's January 24, 1863, issue in the wake of Lincoln's January 1 Emancipation Proclamation (above).
Something I find interesting is that Lincoln did not himself originally want to draft and ratify the Emancipation Proclamation, his party had to pressure him because America at the time was Progressive. I wonder if Nast knew of this, because Lincoln was often mentioned or illustrated in his cartoons.