At the end of the 19th century, family members and associates of abolitionist William Lloyd Garrison donated a number of his letters and other documents to the Boston Public Library, which housed them in its then-new Anti-Slavery Collection. That archive now includes roughly 40,000 items—letters, pamphlets, books, memorabilia, and even a copy of every issue of Garrison’s newspaper The Liberator—written by leading abolitionists between the 1830s and 1870s.

Since there’s no easy way for people to search the mostly handwritten collection, the library is asking volunteers to help transcribe some documents online. After you sign in to the Anti-Slavery Manuscripts project, you’ll be given a manuscript to type out, one line at a time. If another person has already transcribed that particular page, it will be underlined in red, and you can click on each line to either confirm their transcription or enter your own. As Lifehacker explains, having multiple people double-checking each other’s work helps ensure the library ends up with the most accurate version of every document.

Apparently, William Lloyd Garrison called his wife "Wife."Anti-Slavery Collection, Boston Public Library // No Known Copyright Restrictions

Though the manuscripts are written in English, deciphering the penmanship of some 19th-century writers is enough to make you feel like a cryptologist. There’s a chat feature so you can discuss your quandaries and transcriptions with other participants after you’ve submitted a document.

While many of the anti-slavery activists you’ll come across in the project were based in Massachusetts—including Theodore Parker, Wendell Phillips, Lydia Maria Child, and Maria Weston Chapman—the archive also contains the papers of prominent British and Irish abolitionists who supported the American cause, like John Bishop Estlin and Harriett Martineau.

Altogether, the Anti-Slavery Collection paints a comprehensive picture of the abolitionist movement leading up to, during, and after the Civil War, shedding light on how people felt about women’s participation in the efforts and what opposition they faced from proponents of slavery.

You can find out more about the collection here, and start transcribing here.

[h/t Lifehacker]