Barack Obama was the fifth African-American Senator in U.S. history. The sequence was: Hiram Revels (1870, 1st), Blanche K. Bruce (1875, 2nd), Edward Brooke (1967, 3rd), Carol Moseley Braun (1993, 4th), and Barack Obama (2005, 5th). Options A, B, and C are incorrect as they misrepresent the historical count.