The Comic Strip Library is a digital library containing a collection of public domain comic strips. Everything in the collection predates 1923 and is no longer under copyright in the United States. Currently the Comic Strip Library is more of a proof-of-concept and a work-in-progress than a fully realized project, but the foundations are there to build on. Unlike many comic databases which are indexed by date alone, the comics in the Comic Strip Library are thoroughly cataloged.
Thank you, Zachary Chavez.