Born and mostly educated in Rome, Santillana moved to the United States in 1936 and became a naturalized US citizen in 1945. In 1941 he commenced his academic career at the Massachusetts Institute of Technology, becoming an Assistant Professor the following year. From 1943 to 1945 he served in the United States Army as a war correspondent. Following the war, in 1945 he returned to MIT and was made an Associate Professor in 1948, the year he was married. He became a full Professor of the History of Science in the School of Humanities in 1954. In 1969, he published a book entitled: Hamlet's Mill, An Essay on Myth and the Frame of Time with Dr. Hertha von Dechend. This book focused upon the understanding of the connection between the mythological stories of Pharaonic Egypt, Babylon, Greece, Christianity, etc. and the ancient observations pertaining to the stars, planets and, most notably, the 26,000 year precession of the equinoxes. He died at Beverly, Massachusetts, in 1974.