The definitive fourth edition of her religious reference work appeared as 'A Dictionary of All Religions and Religious Denominations.'
In 1817, the fourth and most comprehensive edition of Hannah Adams's landmark reference work appeared under the title "A Dictionary of All Religions and Religious Denominations". This edition represented decades of revision and expansion since the original 1784 publication, incorporating new sects, updated scholarship, and refinements based on reader feedback and Adams's own ongoing research.
By this point, Adams had cultivated correspondents and readers across the United States and Britain, and the book was recognized as a standard reference on comparative religion in both American and European libraries. Its structure—an alphabetical, descriptive catalog of religious groups—anticipated later encyclopedic approaches to religious studies and was praised for its relative objectivity in an era of intense denominational rivalry.
The 1817 edition cemented Adams's standing as one of the foremost scholars of comparative religion in the English-speaking world, a remarkable achievement for a self-taught woman without formal academic training or institutional affiliation. It also underscores her persistence: over more than three decades she continued to revise and improve the work, treating it as a living scholarly project rather than a single fixed publication.