From Parapolitical: The U.S. National Security Agency last month released a 1991 historical summary detailing the U.S. State Department’s first use of the Trans-Atlantic Telegraph Cable to send an encrypted message , which was transmitted on November 24, 1866, from Washington to Paris at a cost of nearly $20,000. The astronomical expense of the cable – the State Department’s telegraph bills up to that point had averaged less than $100 per month – was due in part to the telegram’s incredible length of more than 3,500 words. That length, in turn, was necessitated by the cumbersome, “unbreakable” code the U.S. government had used for the preceding 63 years and prompted the introduction of a new, short code. The short code proved too difficult for recipients to decipher and was, in turn, abandoned in 1876.
The State Department’s original, $20,000 telegram was a demand to Emperor Napoleon III for the timely evacuation of French troops from Mexico.