Drydock Number One, Norfolk Naval Shipyard

Drydock Number One, Norfolk Naval Shipyard, also known as Drydock No. 1, is the site where the USS Merrimack was modified to be the Confederate Navy ironclad CSS Virginia. It is now included within the Norfolk Naval Shipyard. It remains in use.

The drydock measures 319.5 ft in length, and is built of Massachusetts granite, stepped to allow access 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 1833, when the USS Delaware was drydocked for recommissioning, the first time a large vessel was drydocked in the United States. During the American Civil War 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 ft with a 39.33 ft beam. Depth is 30 ft. 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 in 1971.