The Harvard College Observatory (HCO) is an institution managing a complex of buildings and multiple instruments used for astronomical research by the Harvard University Department of Astronomy. It is located in Cambridge, Massachusetts, and was founded in 1839. Harvard College Observatory is historically important to astronomy, as many women including Annie Jump Cannon, Henrietta Swan Leavitt, Cecilia Payne-Gaposchkin, and Williamina Fleming performed pivotal stellar classification research. Detroit Publishing Company, 1900 (cropped and cleaned).