He graduated from Amherst College in 1865 and spent the next three years studying law.

After one year Moulton chose to leave the state legislature and focus full-time on his law practice.

[4] On December 31, 1882 he was appointed by Governor John Davis Long to serve as Essex County District Attorney.

[4][5] Moulton was appointed United States Attorney for the District of Massachusetts on March 20, 1901 by President William McKinley.

[6] Moulton died unexpectedly on the morning of December 4, 1905 at his home in Salem, Massachusetts.