John Payson Williston Observatory stands at the highest point on the Mount Holyoke College campus and has served the college’s astronomy program since its construction in 1881. Modest in size, it is significant for its continued academic use and for housing a rare eight-inch Alvan Clark refractor telescope. That instrument was made shortly before Clark’s death in 1887, adding to the observatory’s historical importance. Maintained and operated by the Mount Holyoke College Astronomy Department, the building continues to support astronomy on campus.