In December 2013, archeological curator Sara Rivers Cofield bought a Victorian-era silk bustle dress from an antique mall in Maine. When Sara examined the dress, she found a hidden pocket that contained mysterious handwritten messages that appeared to be some sort of code. Since then, codebreakers have tried to solve the messages without success. The so-called "Silk Dress cryptogram" became one of the top 50 unsolved codes and ciphers in the world.

The breakthrough came during the holiday season of 2022-23, when Wayne Chan, an analyst with the Centre for Earth Observation Science at the University of Manitoba, discovered that the messages were encoded using a 19th-century telegraphic weather code used by the United States Army Signal Corps, which served as the national weather service for the U.S. during the late 1800s.

The messages turned out to be weather observations from a number of stations in the U.S. and Canada for a particular day in 1888, including one from the University of Manitoba's St. John's College, which was the official weather station for Winnipeg at the time. The code was used to compress the weather reports so that they could be transmitted by telegraph more economically, as messages were charged by the word.

For more information, you can watch a 17-minute graphic novelization of the solution, or read the research article.

For the backstory about how Sara discovered the messages in the dress, please see her blog.