Hartwell ranked high as a sinologist. He spoke the Fuzhou dialect with fluency, and was one of the proposers of the romanization of that dialect. In addition to preaching the Gospel, he translated one fourth of the New Testament into the Fuzhou colloquial, composed the Three Character and the Four Character Classics in the same dialect, and various tracts and books (including the 2nd edition of the Dictionary of the Foochow Dialect). He also prepared many textbooks for schools (including one series of the so-called Hongkong Readers), wrote a book on Meteorology, and contributed articles on temperance to English and American journals.
The fiftieth anniversary of Hartwell's arrival at Fuzhou was celebrated on May 26, 1903, a full account of which was issued from the Foochow Mission Press in February, 1904, in a volume entitled Jubilee Notes.
Hartwell was married twice during his life. On September 6, 1852, he married his first wife Lucy E. Stearns, who died July 10, 1883, in Fuzhou. In 1885 he married his second wife Hannah Louisa Plimpton Peet Hartwell. Hartwell died of heart failure in Fuzhou on January 30, 1905. At the time of his death he was the senior missionary of the American Board in China. His wife died 3 years afterwards. His daughter, Emily Susan Hartwell, remained in the field until 1937.
Rev. Charles Hartwell with Chinese preachers and booksellers, 1900
Charles Hartwell with Foochow College faculty, 1903
