The Carnegie-founded Mt. Wilson Observatory was home to the most important astronomical discoveries of the 20th century. Carnegie astronomer Edwin Hubble shattered our old concepts of the universe with his discoveries that there are galaxies other than the Milky Way and that universe is expanding. The Carnegie Observatories continues to be at the forefront of astronomy today.

It all began in 1904 when solar scientist George Ellery Hale received support from the newly formed Carnegie Institution to found the Mount Wilson Solar Observatory in the mountains near Pasadena, California. Hale was inventor of the spectroheliograph, discoverer of solar magnetism, and one of the founders of modern astrophysics. He pushed beyond the descriptive astronomy of the day to understand the internal physics of the Sun and stars. Following the first Mt. Wilson solar telescopes, he embarked on constructing the largest telescopes in the world: first the 60-inch, then the 100-inch Hooker telescope, both of which redefined astronomy and what we know of the universe.

 

Many historic discoveries were made by Carnegie Institution astronomers at the Mt. Wilson Observatories: Harlow Shapley’s mapping of the collections of stars called globular clusters in the Milky Way, Hubble’s discovery of the expanding universe, Walter Baade’s first recognition that there are distinct populations of stars, and Allan Sandage’s contributions to theories of stellar structure and evolution.

In 1928 the Carnegie and Mount Wilson astronomers persuaded the Rockefeller Foundation to fund a 200-inch telescope on Palomar Mountain. Title was given to the California Institute of Technology, which joined with Carnegie to form the Mount Wilson and Palomar Observatories, a partnership that lasted until 1980. In 1986, as light pollution encroached from the Los Angeles basin, day-to-day operation of the Mt. Wilson telescopes was transferred by Carnegie to the Mount Wilson Institute. and Las Campanas, Chile, became Carnegie's principal observing site. The newest additions there,  the twin 6.5-meter Magellan telescopes, are remarkable members of the latest generation of giant telescopes.

The main offices of the Carnegie Observatories are located on Santa Barbara Street in Pasadena, California, with about 65 scientific, support, and technical staff in residence. Fifty-two hundred miles southeast of Pasadena, about a dozen scientists and administrative personnel work in the offices of the Las Campanas Observatory located in the coastal resort city of La Serena, Chile. The observatory itself is located approximately 100 kilometers north of La Serena, Chile, at an altitude of 2,400 meters.
Today Carnegie astronomers are leaders in many areas of astronomy from stellar evolution, dark matter, dark energy, to the large scale structure of the universe. Director Wendy Freedman is also board chair of the Giant Magellan Telescope Corporation, a partnership to build the one of the next generation of super telescopes. She recently received the Gruber prize in cosmology for her role defining the rate at which the universe is expanding. Other prominent astronomers can be found here. 

For more about the history of the Carnegie Observatories, see this link and books below:

 

Good Seeing: A Century of Science at the Carnegie Institution of Washington, 1902-2002, by Trefil and Hazen

Centennial History of the Carnegie Institution of Washington; Volume 1, The Mount Wilson Observatory, by Sandage