Drydock Number One, Norfolk Naval Shipyard (in the city of Portsmouth) is the oldest, continuously used dry dock in the United States. This impressive engineering work was one of the first two drydocks erected by the U.S. government. Begun in 1827 and completed in 1834, Drydock Number One remains in regular use at the Norfolk Naval Shipyard, the nation’s oldest shipyard, established in 1767. Though a monumental construction project during the early-19th-century, the size and scale of the drydock is much smaller than its current counterparts. Drydock Number One was constructed of large blocks of Massachusetts granite with sides built up in a series of giant tiers. The overall length of the drydock is 319-1/2 feet. The drydock originally featured a wooden gate and floating caisson system that was replaced in 1924, and again in 2015. Changes to the drydock have allowed its continued use as maritime technology evolved, however, they have not resulted in the loss of character defining features and did not alter the resource in ways that compromised its historic integrity.