Muhammad Ali was one of the best-known men of the 20th century, a three-time heavyweight boxing champion who captivated millions of fans throughout the world with his mesmerizing combination of speed, grace, and power in the ring, and charm and playful boasting outside of it. At the height of his fame, he took American life — the racial prejudices, the religious biases, the role of celebrities, the role of sports in society — and refashioned it in his own image.