The Library of Congress held thousands of items considered to be pornographic or obscene in its restricted Delta Collection. It remains unclear as to when the collection was first formed, but it may have been as early as the 1880s, and it remained restricted until 1964. The collection included books, motion pictures, photographs, playing cards, handkerchiefs, and other materials. Many of the materials had been seized by the Customs Bureau and the Postal Service, and others were obtained through the Copyright Office and were considered vulnerable to theft and damage.

The Delta Collection served to protect materials from mutilation, preserve the cultural record, protect citizens from harmful obscenity, and serve as a repository of sample materials for consultation by federal agencies.

Registered members of the public could view materials in the Delta Collection, but only by requesting specific titles from the librarian. There was no public catalog. This project brings the book titles into view in a single catalog. Wherever possible, links to full text are provided.