He married his first wife, Emma Juel Sill, on September 29, 1887; the couple had one son, Noah T. Clarke. In 1894 he was named professor of Geology and Mineralogy at the Rensselaer Polytechnic Institute. He married his second wife, Fannie V. Bosler, in 1895. Following the death of James Hall in 1898, Clarke was named New York State Paleontologist and was put in charge of a geological survey of New York. In 1904 he became the State Geologist and Paleontologist, Director of the State Museum, and Director of the Science Division of the Education Department. He was named the first president of the Paleontological Society in 1908, then served as vice president of the Geological Society of America in 1909 and its president in 1916.Fairchild, Herman LeRoy, 1932, The Geological Society of America 1888-1930, a Chapter in Earth Science History: New York, The Geological Society of America, 232 p.Eckel, Edwin, 1982, GSA Memoir 155, The Geological Society of America — Life History of a Learned Society: Boulder, Colorado, Geological Society of America Memoir 155, 168 p., .
