Articles on the Anthology’s grand opening ran in both the New York Times and New York magazine in late November. Plus, the Anthology itself ran a full page ad in the Times with the screening calendar of its first four days. Through that printed material, those early days can be pretty well reconstructed.
The Anthology itself says that it opened its doors on November 30, 1970; but, according to an article in the Times the previous day by film critic Vincent Canby, that opening was an invitation-only event at which work by George Méliès, Joseph Cornell, Jerome Hill and Harry Smith was screened. Jonas Mekas