The observatory of the University of Chicago at Williams Bay, Wisconsin, on the shores of Lake Geneva, at an altitude of 330 m. It was founded in 1897 by G. E. Hale with a grant from the American businessman Charles Tyson Yerkes (1837–1905). Its main instrument is the world’s largest refractor, aperture 40 inches (1.02 m), opened in 1897. It also has a 1-m reflector, opened in 1967, with adaptive optics added in 1994.

http://astro.uchicago.edu/yerkes/ Official observatory website.