Joseph Winlock was a nineteenth-century mathematician and astronomer and a founding member of the National Academy of Sciences. He led expeditions to view solar eclipses, modernized the Harvard Observatory, and made contributions in the field of double stars. He began his career working for the American Ephemeris and Nautical Almanac, a record of astronomical data for the sun, moon, stars, and planets used both by astronomers and in navigation. He briefly worked for the U. S. Naval Observatory before returning to the Ephemeris and Almanac as director in 1857. After a period at the U.S. Naval Academy, he moved to Harvard University and became the Phillips Professor of Astronomy and director of the Harvard Observatory.