Yerkes Observatory

The observatory grew from astronomer George Ellery Hale’s effort to build a major research facility. Yerkes Observatory’s institutional history traces the idea to 1892, when Hale learned of two unused 40-inch lens blanks, and credits University of Chicago president William Rainey Harper and businessman Charles Tyson Yerkes with supporting the project. Construction began in 1895, and the observatory opened in 1897 at Williams Bay on Geneva Lake in Wisconsin.

Yerkes is especially known for its 40-inch refracting telescope, commonly called the Great Refractor. A refractor uses lenses to gather and focus light, in contrast to a reflecting telescope, which uses mirrors. At its dedication in 1897, the Yerkes instrument was the largest refracting telescope in the world, a distinction that reflected the scale of late-19th-century efforts to extend astronomical observation. The observatory’s work brought together telescope research, experimentation, photography and education.

Yerkes became an important setting for astronomical research and training. Its institutional history documents generations of astronomers connected to the observatory, among them Edwin Hubble, Nancy Grace Roman and Carl Sagan. The observatory’s photographic legacy is also preserved in the University of Chicago Library’s Yerkes glass-plate collection, a record of the role photographic observation played in astronomy. Claims about the specific discoveries made at the observatory should be tied to their individual researchers and evidence rather than attributed to the building alone.

After more than a century of scientific activity, Yerkes has also become a site of architectural and historical preservation. Its current stewardship emphasizes restoration of the building and grounds, public engagement and the interpretation of its scientific history. The observatory’s legacy therefore combines an influential telescope, institutional research and a continuing public role in communicating astronomy and heritage.