Miller became the editor-in-chief of The New York Times when he was 34, and would remain in that position for the rest of his life (about forty years).

While in college, he had planned to teach Latin, but upon graduation he found employment at the Springfield Republican.

Miller left that paper after around three years and was hired on July 7, 1875, by the New York Times as an assistant to the telegraph editor.

Miller led the creation of a syndicate, the New York Times Publishing Company, which purchased the paper on April 13, 1903.

[5] Miller defended freedom of the press before an investigatory committee in the United States Senate.