The Dearborn Observatory is an astronomical observatory located on the Evanston campus of Northwestern University. The observatory was originally constructed in 1888. In the summer of 1939, Dearborn Observatory had to be moved to make way for the construction of the Technological Institute.
The history of the Dearborn Observatory coincides with the founding of the Chicago Astronomical Society in 1862. In 1863 the society heard of the construction of a 18.5" lens for a telescope, which made it, at the time, the largest refracting telescope in the World. The lens had been commissioned by Frederick Augustus Porter Barnard, the chancellor of the University of Mississippi (later president of Columbia University), who hoped to found an observatory with the new lens. He commissioned the renowned firm of Alvan Clark & Sons of Cambridge, Massachusetts, to construct the lens. However, the American Civil War began before the lens could be delivered to Mississippi. The lens therefore remained in the Clark's shop in Cambridge, where it was eventually put up for sale.
The lens was initially intended for Harvard University, but was bought instead by Chicagoan Thomas Hoyne, a founding member of the Chicago Astronomical Society, for the sum of $11,187. The Chicago Astronomical Society intended the lens for the Old University of Chicago (a precursor to the current University of Chicago) and a tower was constructed on Cottage Grove Avenue around the lens. The structure was named the "Dearborn Observatory" in honor of Mary Ann Haven Dearborn, the deceased wife of J. Young Scammon, principal benefactor of the project. Construction of the observatory began in 1863, and the original Dearborn Observatory was completed two years later. The Observatory was managed by the Old University of Chicago for many years, however financial struggle caused U of C to declare bankruptcy in 1881, and the Chicago Astronomical Society had to do battle in the courts to successfully establish their title to the Dearborn instruments & library.
The close affiliation between Dearborn Observatory and the Chicago Astronomical Society continued until, following the Wall Street Crash of 1929, the Society encountered financial hardship and found it too expensive to maintain the observatory and its equipment. On April 30, 1930, the Chicago Astronomical Society formally relinquished its title to the observatory to Northwestern University, on the condition that the Observatory be open to the public without cost.In 1911, Northwestern decided that the lens needed a more modern mounting, and the original tube and mount were removed. In 1929, these pieces were placed on permanent loan to the new Adler Planetarium, and installed on the planetarium's exhibit floor. The 18.5" lens has remained at Northwestern.In the summer of 1939, the Dearborn Observatory building had to be moved 664 feet southeast to its present location to make way for the construction of the Technological Institute. The latest addition to the observatory was a 38-foot aluminum dome, added in 1997.The telescope is still in active use today and the observatory is used for classroom space, offices and a library.