John H. C. Coffin was a sailor, mathematician, and astronomer in an age when the three areas were closely linked. His 1868 Navigation and Nautical Astronomy was for decades the textbook for navigation at the United States Naval Academy. He was assigned to the U. S. Naval Observatory in Washington, D.C., during its early years and played a great role in its development. Fading eyesight caused him to give up astronomical observation in 1849, though he remained at the observatory until 1855, when he took a position as instructor of mathematics at the U.S. Naval Academy in Annapolis. It was at this time that he began drafting his noted navigation textbook. As one of the few instructors not called to duty during the Civil War, he became effectively the director of all instruction at the Naval Academy for the duration of the war. At the war’s end, he took a position as superintendent with the American Ephemeris and Nautical Almanac, succeeding Joseph Winlock in that role. He was a charter member of the National Academy of Sciences.