All of the sites listed below are less than 50 years old and should be re-examined for national significance in the future.
Kitt Peak National Observatory
Kitt Peak hosts 16 telescopes and represents the largest concentration of astronomical instruments in the world.
U.S. Naval Observatory
This observatory houses a 40-inch Ritchey-Chretien telescope that was originally put into operation by the U.S. Naval Observatory in Washington, DC., in 1934. Due to increasing light and air pollution in Washington the telescope was moved to Flagstaff, Arizona in 1955. This telescope is the last instrument built by George W. Ritchey.
Naval Research Laboratory
Immediately after World War II, apart from the completion in 1946, of the U.S. Army Signal Corps project to detect radar echoes from the moon, the only important work in radio astronomy took place here. Research started by J.P. Hagen, F.T. Haddock, and others represented a highly significant step, leading the way in short wave length radio astronomy, and strongly influencing the pattern of much subsequent research. The 50 ft. parabolic reflector, completed in 1950, was the first radio telescope built to operate at wave lengths down to 1 cm.
Sacramento Peak Solar Observatory
The Sacramento Peak Solar Observatory is found in the Lincoln National Forest and contains a 136-foot tower telescope dedicated to observing the sun.
Kraus Reflector Radio Telescope
This radio telescope, designed by J.D. Kraus, is a long reflector having limited steering, with the long dimension parallel to the ground. This type of telescope was an attractive idea for the economical construction of a large, partially steerable radio telescope.
Arecibo (Radio) Telescope
Site of the world's largest radio astronomy dish. Used for ionospheric studies radar mapping of the moon and planets, and radio astronomy. Arecibo has played a major role in identifying some of the most mysterious signals received on Earth--pulsars, quasars and natural hydrogen emissions from the galaxies.
National Radio Astronomy Observatory
The National Radio Astronomy Observatory came into being in 1955 as a result of a grant from the National Science Foundation to Associated Universities, Inc., to establish a national radio astronomy observatory for scientific research. The first radio telescope constructed at Greenbank was the 85-foot Tatel Telescope. One telescope at this site, the Reber radio telescope, is being recommended for designation in this theme because its significance predates the establishment of the observatory. Another instrument, the 300-foot radio telescope, was under consideration for designation when it collapsed in late 1988.