The first illumination in Oberlin occurred in November 1860 to celebrate the election of Abraham Lincoln as President. However, the longstanding tradition began in May 1903 during the inauguration of Oberlin College President Henry Churchill King. Frederick O. Grover, Professor of Botany, helped mark the occasion by stringing Japanese lanterns on campus. The events of inaugural week were described in the book Inauguration of President Henry Churchill King of Oberlin College, May 13, 1903 (p.19).
The enjoyment of the excercises of Inaugural Week was heightened by the unusually attractive weather which prevailed. The temperature on the morning of Inaugural Day was ideal for such a function as the Inaugural Procession, and the evenings were warm enough for the full appreciation of the campus illuminations which had been arranged by the Committee on Decoration.
Illumination night eventually became a tradition held during commencement. See Robert A. Hasluns article Commencement and Tradition at Oberlin.