After attending classes in the landscape architecture department of Massachusetts Agricultural College in Amherst, Caldwell became a member of the American Society of Landscape Architects (ASLA) in 1916 and went on to practice for many years in the Boston area. He served as a consulting landscape architect at Mount Auburn Cemetery between 1929 and 1937.
Caldwell’s contributions to Mount Auburn reflected a shift in how cemeteries were designed and experienced during the early twentieth century. Drawing from his experience as an estate designer, he employed elements such as lawns bounded by landscape features rather than fences, central water features, statuary, and areas for communal gathering. He also began promoting the use of level marker stones. His designs reflected an approach to circulation within the cemetery that accommodated the automobile. He implemented the re-design of The Lawn (now the Asa Gray Garden), Willow Pond, and Hazel Dell. He also laid out much of the southwest portion of the cemetery.