 Callaghan moved to United States in 1975, where she finished her first novel, "Mothers", in 1978 (published in 1982).The book is composed of monologues telling the stories of three Irishwomen from three generations, exploring marriage, adoption and pregnancy out of wedlock, and female sisterhood.While continuing to write fiction, she also worked as a contributing editor for the "Journal of Irish Literature" from 1975 to 1993, and was associate editor for the first two editions of the "Dictionary of Irish Literature".