Historic Observatories of the United States

The first three large observatories shown on this page were created through the efforts of Chicago native George Ellery Hale (1868-1938). Hale built the largest telescope in the world four times - the 1 meter refractor at Yerkes, the 1.5 meter and 2.5 meter reflectors at Mount Wilson, and the 5 meter reflector at Mount Palomar. He was the first to select observatory sites for their suitability for making observations, not for their proximity to the sponsoring institution.


Dome for 24 inch reflector	Column detail	Main entrance	Column detail

Yerkes Observatory on the banks of Lake Geneva, Wisconsin houses the largest refracting telescope in the world. This one meter (40 inches) diameter lens went into service in 1897, and nothing larger has been built since. The architecture of the observatory is a delight - beautiful baroque decorations are everywhere. The location is equally stunning - on the shores of beautiful Lake Geneva, a delight in summer and absolutely captivating in the fall with its backdrop of vivid, multihued foliage. Is this a great place for an observatory, or what! Well, actually no. To much humidity, to much atmospheric turbulence, to many cloudy days. The experience with Yerkes led Hale to California and the still, dry skies of the San Gabriel mountains.


*2.5 meter Hooker telescope and dome*	Inside 150 ft solar tower

The Mount Wilson Observatory in the San Gabriel Mountains above the Los Angeles basin is by almost any measure the most significant astronomical observatory ever built. Selected for its excellent "seeing" conditions, the site hosted the largest telescope in the world for over 40 years, beginning with the 1.5 meter (60 inch) reflector in 1908 and continuing with the 2.5 meter (100 inch), completed in 1916. Historic "firsts" include the determination that the sun is not in the center of the Milky Way, the discovery that the Milky Way is not the only galaxy in the universe, the discovery that the universe is expanding (deduced from the red-shifted spectra of external galaxies) and the realization that the stars found in the centers of spiral galaxies and those found in their spiral arms form two distinct stellar groups with different physical characteristics (Population I and Population II). Famous astronomers associated with Mt. Wilson include Harlow Shapley, Edwin Hubble and Walter Baade; Albert Einstein, who had a special interest in the red shift findings, made several visits to the dome. Now at the beginning of the 21st century Mount Wilson continues its productive career with state-of-the-art imaging and high resolution accessories for the 2.5 meter telescope and the new CHARA interferometer facility operated by Georgia State University.

The 5 meter reflecting telescope on Mount Palomar in San Diego county was the largest telescope in the world when it went into service in 1949. Although he died before it was finished, Hale was the driving force behind its construction and secured the necessary funding to insure its completion. The 5 meter instrument remained the largest telescope in the world until the Soviet 6 meter reflector was built in the middle 1970s. However, the Soviet telescope had a host of problems which allowed Palomar to remain the largest fully functional telescope until the 10 meter Keck telescope in Hawaii began observations in 1990.


*107" and 82" domes*	*Hobby Eberly Telescope*

McDonald was built in the 1930s and is the last of the great pre-World War II observatories. In addition to the historic 82" reflector it currently has the largest segmented mirror in the world (11 meters). To see more images click on the link below.


5 meter dome at sunset	*5 meter Hale telescope*	Telescope control panel