Fully searchable text of over 58,000 letters and documents of British, American, French, German, and other Enlightenment figures, unpublished or previously published in dozens of critical editions for over 7,000 correspondents, including writers, scientists, booksellers, philosophers, politicians, political thinkers, in original language editions or translation.  The major languages represented are English (45%) and French (45%), with other documents in Dutch, German, Greek, Italian, Latin, Portuguese, Russian, Spanish, and Swedish.

Users can search or browse letters by text keyword, writer, recipient, date, and location and limit by language.  The database contains information about all persons mentioned in the letters, searchable by name, occupation, name, and dates; the sources of manuscripts ("instances") and scholarly annotations (over 250,000) are also searchable, and there are a growing number of external links, including to databases such as the Oxford Dictionary of National Biography available at Rutgers.