Stephen Alexander was a charter member of the Academy and a noted astronomer who contributed greatly to the growth of the discipline at Princeton University, where he stayed for nearly fifty years. Alexander, who graduated from Union College in 1824, acquired a position as a mathematics tutor at Princeton in 1833. He joined the faculty of the university as a professor of astronomy in 1840. Alexander was instrumental in establishing the field as an independent discipline and building Princeton’s Halsted Observatory in 1869. Alexander conducted research on solar eclipses and also published significant research regarding the atmospheres of Jupiter, Venus, and Mercury. Alexander acquired a number of accolades and honors throughout his career, including the presidency of the American Association for the Advancement of Science.