River Styx, a literary organization based in St. Louis and now in its 38th year, presents a monthly reading series and publishes a tri-annual magazine of the same name. Gass served as Chairman of the Literary Advisory Committee, 1982-92, and President of the Board, 1985-88. He helped bring writers such as Susan Sontag and John Barth in for River Styx readings and sponsored events, and has participated in such events himself through the years.

The Special Collections holds the River Styx Collection, spanning from 1973 to 2001, consisting of files on contributors, events, business, governance, ephemera and other materials. Other collections, such as the Jan Garden Castro Papers and the Modern Literature Recorded Multimedia Collection, contain River Styx documents and recordings. The Special Collections is also working with River Styx co-founder Michael Castro to acquire further materials related to this important literary organization.