Clinton Hartley Grattan was born at Wakefield, Massachussetts, United States of America. After receiving a degree from Clark University, Worcester, Grattan moved to New York in 1925 to begin a career in journalism. Grattan visited Australia in 1927, accompanying his actress wife who was performing in a musical. This visit inspired him to learn more about Australian literature. The resulting volume, Australian Literature (1929), was one of the first attempts to analyse the unique Australian character of nineteenth and twentieth century Australian literature. His booklet was noticed by several prominent writers, including Miles Franklin, Nettie Palmer and Katharine Susannah Prichard, enabling him to circulate among Australian intellectuals during subsequent visits. Grattan wrote on various Australian topics for journals such as Australian Quarterly and Harper's Magazine and published in New York the bestselling Introducing Australia (1942). Grattan's study of Australia and the Southwest Pacific culminated in two volumes, The Southwest Pacific to 1900 and The Southwest Pacific since1900, both published in 1963. In 1964 Grattan's large collection of Australian and Southwest Pacific material was bought by The University of Texas at Austin and he accepted the position of curator.
Grattan retired in 1974. In 1977 he received an honorary LL. D from the Australian National University for his contribution to the study of Australian culture. He died in 1980. According to his wish, his ashes were scattered over Sydney Harbour.