The 2nd World Science Fiction Convention (Worldcon), also known as Chicon I, was held on 1–2 September 1940 at the Hotel Chicagoan in Chicago, Illinois, United States.
The convention was chaired by Mark Reinsberg with Erle Korshak (secretary) and Bob Tucker (treasurer) as equal partners.
[5][6] The official event, called the "Science Fiction Masquerade Party", was held in the evening of the first day, with Jack Speer and Milton A. Rothman as the co-masters of ceremonies.
[4] The winner of the Masquerade Party was David Kyle wearing a Ming the Merciless costume, for which he won an Amazing Stories original cover painting.
[8] In second place was Robert A. W. Lowndes wearing a Bar Senestro costume (from the novel The Blind Spot by Austin Hall and Homer Eon Flint).