[3] Stevens began his career as a draftsman, and worked in his father's architectural firm from 1898.
Stevens' son, John Calvin II, had joined the practice seven years earlier.
[3] In 1909, Stevens and his father assisted Carrère and Hastings in designing today's Portland City Hall.
[5] Stevens married Agnes McFadden in 1903, with whom he had three children: Mary Caroline, John Calvin II and Howard Winchester.
[3] He served as secretary and treasurer of the Maine chapter of the American Institute of Architects between 1934 and 1940, and as its president between 1940 and 1946.