The first milestone in the history of a ship is the generally simple ceremony that marks the laying of the keel. Laying the keel or laying down is the formal recognition of the start of a ship's construction. It is marked with a ceremony attended by dignitaries from the shipbuilding company, the US Navy, Ship Sponsor, and Commissioning Committee.
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In earlier times, the event recognized as the keel laying was the initial placement of the central timber making up the backbone of a vessel, called the keel. Keel-related traditions from the times of wooden ships are said to bring luck to the ship during construction and to the captain and crew during her later life. They include placing a newly minted coin under the keel and constructing the ship over it, having the youngest apprentice place the coin, and when the ship is finished, presenting the owners with the oak block on which the keel is laid. The tradition of the placement of coins derives from the mast stepping custom of placing coins under the mast and is believed to date back to Ancient Greece or Ancient Rome and were intended to "pay the ferryman" to convey the souls of the dead across the River Styx should the ship sink.
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As steel ships replaced wooden ones, the central timber gave way to a central steel beam, as was used in the USS Massachusetts (SSN 798). For the prospective USS Massachusetts (SSN 798), the keel laying ceremony included the welding of a commemorative plate on the keep signed by the Ship Sponsor.
The USS Massachusetts (SSN 798) Keel Laying occurred on December 11, 2020 at Newport News Shipbuilding in Virginia.