Sumner, Charles (1811–74), U.S. political leader and opponent of slavery. He was a senator from Massachusetts from 1851 to 1874. As an active abolitionist, he denounced slavery and the South. In 1856 he made a speech in which he accused Senators Andrew P. Butler and Stephen A. Douglas of suppporting slavery. A few days later, Representative Preston S. Brooks, Butler's nephew, accused Sumner of slander and beat him with a cane, wounding him severely. After the Civil War, Sumner proposed stiff treatment of the South, demanding that Southern states could join the Union only after they allowed freed slaves voting rights. He was active in the impeachment of Andrew Johnson.