Initially, it was unclear if the object was actually a pumpkin, as the tower is 173' tall. For pumpkin skeptics and conspiracists, a recent Cornell Chronicle article features a photo of the "Certificate of Authenticity" from the Kingsbury Commission (which intensively studied the matter) that unequivocally states: "It's a pumpkin." A thorough and fascinating summary of the events, and speculation, surrounding the incident has also recently been published by Atlas Obscura.
To mark the 20th anniversary, Cornell University Library is hosting a "PumpkinCam Redux," with much--but not all--of the content of the original website. Bits and cucurbits both decay, after all. Happy Halloween!
Note: the photo above is a Cornell University file photo.