Who was the first to determine the sequence of a polypeptide?

Sanger was the first to determine the sequence of a polypeptide. Mature insulin consists of the 21-residue A chain and the 30-residue B chain linked by disulfide bonds. Frederick Sanger reduced the disulfide bonds, separated the A and B chains, and cleaved each chain into smaller peptides using trypsin, chymotrypsin, and pepsin. Ref: Harper’s illustrated biochemistry. 30th edition page no: 29