Starting in 1918, Coffin served as landscape architect for the Day and Klauder campus redevelopment, and her eight-foot-long plan for the grounds survives (1919). This pioneering woman professional was brought from New York City by H. Rodney Sharp and other du Ponts on the board, for whom she had provided estate garden designs (at Winterthur, CH10; St. Amour, CH23; and Gibraltar, WL94). Historian Nancy Fleming writes (1995) that the campus is her “most significant professional achievement. . . . Much of Coffin's plan survives: the circulation system of paths and drives, the lamp-posts, the wall enclosing the women's campus, the oval, and the Magnolia Circle, which disguises the misalignment of axes between the men's and women's colleges. The rows of honey locust on the women's campus and the allee of paulownia on the oval are also intact.” Actually, the oval planned in 1919 was not laid out until 1935, and then as a rectangle. Its paulownia trees—recently replanted—are a rarity on college campuses but were a du Pont family favorite. Magnolia Circle was also established in 1935, an enlarged version of the small circle originally proposed; it was redesigned in 2005 and given a brick central fountain. To the east survives a section of Coffin's arboretum.