Deciphering a Mystery Letter

Sometimes in July 1775, a Massachusetts man entrusted a letter to his mistress—or perhaps one of his mistresses. He told her to send it into British-occupied Boston by way of Newport. That Rhode Island port was still open for business, with Patriot and Loyalist officials in a grudging stalemate and the Royal Navy, merchant ships, and smugglers all sailing in and out of the harbor.

That woman, who has never been identified, sent the letter to an old boyfriend, the Newport baker Godfrey Wenwood (sometimes spelled Wainwood), and asked him to pass it on. He became suspicious because the letter was in code; there was, after all, a war on. On the other hand, he was about to get married, and may not have wanted to reveal an old affair by taking the document to the authorities. So he sat on it.

In September, the lady wrote to Wenwood again:

i much wonder you never Sent wot you promest to send if you Did i never reseve it so pray Lett me know By the first orpurtunty wen you expet to be hear & at he Same time whether you ever senty me that & wether you ever got a answer from my sister i am alittle unesey that you never rote thar is aserten person hear wants to Sea you verey much. . . .

if you righ Direct your Lettr to mr Ewerd Harton Living on Mr. Apthorps farm in Littel Cambrig

“Little Cambridge” was then the name for Brighton. “Apthorp’s farm” was probably the estate of John Apthorp, youngest son of a wealthy Anglican family; he and his wife had been lost at sea in 1772, leaving three children to be raised by relatives. The name of Edward/Edmund Horton appears on official documents from Cambridge in this period.

Wenwood talked with a friend who taught school, and together they went to the Secretary of the Rhode Island colony, Henry Ward. In Massachusetts, the governor, secretary, and other executive-branch officials were appointed in London, but in Rhode Island (and Connecticut) they were elected by the legislature. Ward was therefore a Patriot, not a friend of the Crown. He sent Wenwood with his letter to Gen. Nathanael Greene, the highest-ranking Rhode Islander in the Continental Army around Boston.

Greene read Ward’s letter, heard Wenwood’s story, and quickly took the baker and his packet to army headquarters in Cambridge. After a private conference with Gen. George Washington and Greene, Wenwood agreed to visit his old girlfriend and try to learn who had given her that coded letter. He failed. Washington ordered the woman to be brought to headquarters. Gen. Israel Putnam personally delivered her, mounted behind him on his horse. Washington used the weight of his authority to convince her to reveal the man behind the coded letter: Dr. Benjamin Church, Jr.

For years, Church had been one of Boston’s leading Whigs, privy to their most secret meetings. In July, he had become the head of the Continental Army’s hospital. Washington summoned him immediately. Dr. Church admitted that he wrote the letter, saying it was really intended for his brother-in-law, the Loyalist printer John Fleeming. He declined to decipher it, though.

Washington sought men familiar with codes. One volunteer was the Rev. Samuel West, a big, untidy minister from Dartmouth (now New Bedford); he was attached to the Continental Army as a chaplain. Another was Elbridge Gerry, the Marblehead merchant and politician, who also recruited Col. Elisha Porter of Hadley. All were Harvard graduates; West was even in Church’s college class.

Dr. Church’s letter turned out to be in a simple substitution cipher, one symbol for each letter of the alphabet. And since he (unlike his mistress) wrote in standard English, the proportions and patterns of the symbols matched regular English prose. Trying out the most common letters in place of the most common symbols, West and the Gerry-Porter team produced two independent decodings of the text. On 3 October, Washington received the two translations. They matched exactly.

COMING UP: What Dr. Benjamin Church’s secret letter said. (Click on the image above for a large digital copy of its first page from the George Washington Papers at the Library of Congress.)