Martin Luther King Jr. was born Jan.15, 1929. But the name on his original birth certificate — filed April 12, 1934, five years after King was born — was not Martin. Nor was it Luther. In fact, for the first years of his life, he was Michael King. And it wasn’t until he was 28 that, on July 23, 1957, his birth certificate was revised. The name Michael was crossed out, next to which someone printed carefully in black ink: “Martin Luther, Jr.” The story of how Michael became Martin began in 1934 when King’s father, who then was known...