When scholars set out to create what would become the Oxford English Dictionary, they faced a rather large problem: How do you document the history of every word in the English language?

Their solution was unexpectedly modern. They crowdsourced it.

Beginning in the 19th century, volunteers were asked to read books and send in quotations showing particular words in use. Thousands of people participated, eventually supplying millions of handwritten quotation slips that helped the dictionary’s editors trace when words appeared and how their meanings changed over time.

James Murray, who became the dictionary’s principal editor in 1879, spent decades sorting through this mountain of evidence from a corrugated-iron workspace behind his Oxford home known as the Scriptorium.

One of his most dedicated contributors had an unusual mailing address.

William Chester Minor, an American surgeon and Civil War veteran, sent Murray thousands of useful quotations while confined at Broadmoor, a psychiatric hospital in England, after killing a man. Murray eventually learned where his prolific contributor was living, and the two developed a long friendship.

The first installment of the dictionary appeared in 1884. The complete first edition was not finished until 1928, more than 70 years after the project began.

Long before Wikipedia, one of the world's great reference works was being assembled with help from thousands of people reading at home and mailing in what they found.