From the Spring 1998 issue of the Alumnae Quarterly:
May Fete was officially sanctioned as a College event at the time of President Woolley's 1901 inauguration. Each year thereafter the scenes and costuming depicting specific themes became more and more elaborate. Huge audiences observed casts of hundreds acting in woodland pantomines on Pageant Field (the area behind today's amphitheater).Each pageant's final scene included the coronation of the May Queen - "the fairest" senior selected by the student body. At one time tradition dictated that the Queen be a brunette in odd years and a blonde in even. A 1947 rule stipulated that she stand at least five feet five inches tall. Each Queen of the May was, however, always the one who received the most votes, and the six runners-up comprised her court. Her identity remained a well-guarded secret until the moment after the flower-laden young women were presented to the onlookers.
The last full fete was held in 1949, but May Queens continued to be crowned at Mount Holyoke until 1967 when the tradition ended. Family Weekend, currently an annual campus event, is a direct descendant of the May festivities.
May Fetes were also popular at other colleges, and I have a few items from other campus celebrations of May as well.