Military secrecy was a bit lax during the American Civil War, by today’s standards, but contractor deadlines were a lot tighter.
The technology that revolutionized naval warfare began with a five-sentence message delivered to The New York Times 150 years ago, on Aug. 9, 1861, and the information was not exactly classified. It was an advertisement placed by the Union Navy, to appear the following six days, under the heading “Iron-Clad Steam Vessels.”
Source: A Brief Dry Spell for the U.S.S. Monitor’s Ironclad Turret