The Smithsonian Astrophysical Observatory (SAO) is a research bureau of the Smithsonian Institution, which was created by Congress in 1846 to carry out the bequest of Englishman James Smithson "to found at Washington ... an establishment for the increase and diffusion of knowledge..." As an independent trust establishment of the United States government, the Institution today conducts scientific and scholarly research, administers national collections, and provides public service, education, and outreach programs supported by Congressional appropriations, trust endowments and revenues, and private contracts, grants, and gifts.

Perhaps because James Smithson was a scientist, it was natural that he envisioned an institution for the "increase" as well as the "diffusion" of knowledge. Although Smithson's will did not specify a particular research focus, former President John Quincy Adams sought in 1838 to have Smithson's funds applied to the establishment of a national astronomical observatory, or what he called "a lighthouse of the skies." Other interests prevailed at that time, and the Institution became a diverse array of museums and laboratories.

It was not until 1890 that SAO was founded by Samuel Pierpont Langley, the Institution's third Secretary, primarily for studies of the Sun. Langley is remembered today as an aeronautical pioneer, but he was trained as an astronomer and was the first American scientist to perceive "astrophysics" as a distinct field. Langley invented the bolometer and discovered infrared radiation from the Sun. He foreshadowed modern concerns about climate change by searching for links between solar and terrestrial phenomena.

In 1955, SAO moved from Washington, D.C., to Cambridge, Massachusetts, to affiliate with the Harvard College Observatory and to expand its staff, facilities, and, most important, its scientific scope. Fred Whipple, the first director of SAO in this new era, accepted a national challenge to create a worldwide satellite-tracking network, a decision that would establish SAO as a pioneer―and leader―in space science research. In 1973, the ties between Smithsonian and Harvard were strengthened and formalized by the creation of the joint Harvard-Smithsonian Center for Astrophysics (CfA).

Today―more than 30 years later―SAO is part of what is arguably the largest and most diverse astrophysical institution in the world, where the combined staff now numbering more than 300 scientists carries out a broad program of research in astronomy, astrophysics, and earth and space sciences.

SAO's pioneering efforts in the development of orbiting observatories and large ground-based telescopes, the application of computers to astrophysical problems, and the integration of laboratory measurements, theoretical astrophysics, and observations across the electromagnetic spectrum have contributed much to unveiling the secrets of the universe. From measuring the slow drift of the Earth's continents to charting the thousands-of-kilometers-per-second recession of galaxies, SAO scientists remain dedicated to the increase of knowledge about those physical processes that shape the natural world, and to the diffusion of this knowledge to the scientific community, to teachers and students, and to the general public.