An observatory in Williams Bay, Wisconsin, which belongs to the Department of Astronomy and Astrophysics of the University of Chicago. The telescope housed at the observatory is the largest refracting telescope ever built, with an objective lens 1 metre 40 inches in diameter. It was constructed between 1895 and 1897. The telescope was largely the brainchild of George Ellery Hale, who later became the driving force behind the 2.5-metre 100-inch Hooker Telescope at Mount Wilson and the 5-metre 200-inch Palomar telescope. In association with William Rainey Harper, he persuaded the Chicago millionaire Charles Yerkes to finance the entire project. The lens components were already in existence, having been manufactured for another project that never came to fruition. The mechanical parts of the telescope were constructed by Warner and Swasey of Cleveland, Ohio. The building is noted for its ornate design by the architect Henry Ives Cobb. The 40-inch telescope is still used in some of the Department’s research programmes.