His intense studies into history allowed Kelly to bring to his work a degree of detail that makes his drawings and statues noteworthy.

He worked as a wood engraver, as an illustrator for Harper's Monthly and other magazines, and for a time shared a studio with artist Edwin Austin Abbey.

[2] Kelly, Daniel Chester French, and Cyrus Edwin Dallin were the finalists in an 1883 national design competition to model an equestrian statue of Paul Revere for Boston, Massachusetts.

He had a difficult time finding models who did not have mustaches or beards – then being worn by most men of that era – so he prevailed upon a friend from nearby Menlo Park, New Jersey, to pose for him.

On October 1, 2006, a black granite monument with Kelly's image carved into it and the words, "A Sculptor of American History" was placed over the artist's previously unmarked grave.