The familiar orange book, The Nautical Almanac, along with the chronometer, the sextant, a steady hand and a keen eye, are the resources needed to navigate by the stars. Even today celestial navigation remains a critical backup to GPS and other electronic navigation systems.

The British first published the Nautical Almanac and Astronomical Ephemeris in 1766, with data for 1767. In the United States, the naval appropriations act of 3 March 1849 authorized the preparation and publication of the data necessary for navigation. For this purpose the U.S. Nautical Almanac Office was established in the same year. The American Ephemeris and Nautical Almanac was first published in 1852, with data for 1855. The Nautical Almanac has been published separate from its parent publication in the UK since 1914, and in the U.S. since 1916. Since the unification of the Almanacs in 1958 the U.S. Nautical Almanac Office has produced The Nautical Almanac in full collaboration with Her Majesty's Nautical Almanac Office.

Initially the almanacs provided the data required for the method of lunar distances, a technically demanding and mathematically complex method of determining longitude before the invention of accurate clocks for shipboard use. The common availability of precise chronometers on ships beginning in the early 1800s, and the development of methods of "sight reduction" by Sumner, St.-Hilaire and others, provided an easier procedure for navigators to determine their position at sea. The almanacs provided the necessary data for these methods.