Drydock Number One, Norfolk Naval Shipyard, also known as Drydock No. 1,
is the site where the USS Merrimack

USS Merrimack (1855)

USS Merrimack was a frigate and sailing vessel of the United States Navy, best known as the hull upon which the ironclad warship, CSS Virginia was constructed during the American Civil War...

 was modified to be the Confederate Navy

Confederate States Navy

The Confederate States Navy was the naval branch of the Confederate States armed forces established by an act of the Confederate Congress on February 21, 1861. It was responsible for Confederate naval operations during the American Civil War...

 ironclad

Ironclad warship

An ironclad was a steam-propelled warship in the early part of the second half of the 19th century, protected by iron or steel armor plates. The ironclad was developed as a result of the vulnerability of wooden warships to explosive or incendiary shells. The first ironclad battleship, La Gloire,...

 CSS Virginia

CSS Virginia

CSS Virginia was the first steam-powered ironclad warship of the Confederate States Navy, built during the first year of the American Civil War; she was constructed as a casemate ironclad using the raised and cut down original lower hull and steam engines of the scuttled . Virginia was one of the...

. It is now included within the Norfolk Naval Shipyard

Norfolk Naval Shipyard

The Norfolk Naval Shipyard, often called the Norfolk Navy Yard and abbreviated as NNSY, is a U.S. Navy facility in Portsmouth, Virginia, for building, remodeling, and repairing the Navy's ships. It's the oldest and largest industrial facility that belongs to the U.S. Navy as well as the most...

. It remains in use.

The drydock measures 319.5 feet (97.4 m) in length, and is built of Massachusetts granite

Granite

Granite is a common and widely occurring type of intrusive, felsic, igneous rock. Granite usually has a medium- to coarse-grained texture. Occasionally some individual crystals are larger than the groundmass, in which case the texture is known as porphyritic. A granitic rock with a porphyritic...

, stepped to allow acces to and bracing of ships under repair. Original cost was $974,365.65, a very high price for 1827, when work was started. The project was completed in 1834. However, the drydock was first used in June of 1833, when the USS Delaware

USS Delaware (1820)

The third USS Delaware of the United States Navy was a 74-gun ship of the line, named for the state of Delaware.She was laid down at Norfolk Navy Yard in August 1817 and launched on 21 October 1820...

 was drydocked for recommissioning, the first time a large vessel was drydocked in the United States. During the American Civil War

American Civil War

The American Civil War was a civil war fought in the United States of America. In response to the election of Abraham Lincoln as President of the United States, 11 southern slave states declared their secession from the United States and formed the Confederate States of America ; the other 25...

 the USS Merrimac was rebuilt in the drydock to become the CSS Virginia ironclad.

The drydock can accommodate a maximum vessel length of 291.6 feet (88.9 m) with a 39.33 feet (12 m) beam. Depth is 30 feet (9.1 m). Primarily used for service craft, the dock can be dewatered in 40 minutes and flooded in 90 minutes

It was declared a National Historic Landmark

National Historic Landmark

A National Historic Landmark is a building, site, structure, object, or district, that is officially recognized by the United States government for its historical significance...

in 1971.