William Miller was born on February 15, 1782, in Pittsfield, Massachusetts (USA). His parents were William and Pauline Miller. He was the eldest of sixteen children. During his adolescence, William developed a deep love for reading and learning. Since there weren't many books in his house, he borrowed some from neighbors.

William Miller embraced the ideas of Deism for twelve long years. During that time, he became a Freemason and attained the highest degree available to him. In 1818, William Miller came to the conclusion that Jesus would return to this world in 1843. At first, he didn't want to accept this finding, but eventually, he did.