What is the "oldest" building on campus?

Students sit at lab stations in the Botany II Lab course in April of 1930 in the Botany building. Old Botany is now the oldest structure on campus whose exterior has not undergone significant exterior renovation. Stories float around campus that late at night, the spirit of the wife of President George Atherton, Frances, can be seen with the light on in the attic of Old Botany, keeping watch over her husband's grave, just across the street.