In preparation for World War II, the Brooklyn Navy Yard was extensively reconstructed.
The Navy Yard was expanded slightly to the west by 1.5 acres (0.61 ha), bringing its total area to 356 acres (144 ha), and parts of the mid-19th-century street grid were eliminated in favor of new developments.
These structures included the construction of an 800-by-100-foot (244 by 30 m), single-story turret-and-erection shop; the expansion of the Connecticut building ways; and lengthening of Dry Dock 4.
By 1939, the yard contained more than five miles (8.0 km) of paved streets, four drydocks ranging in length from 326 to 700 ft (99 to 213 m), two steel shipways, and six pontoons and cylindrical floats for salvage work, barracks for marines, a power plant, a large radio station, and a railroad spur, as well as foundries, machine shops, and warehouses.
The new construction involved extensive landfilling operations, some of which yielded artifacts that were centuries old.
In one instance, a Civil War-era prison brig was found eight feet underground, while in another, workers unearthed a skeleton thought to be from one of the prison ship martyrs.

The naval shipyards in Brooklyn and Philadelphia were designated for the construction of battleships.
The first World War II-era battleship built at Brooklyn Navy Yard was North Carolina, which started construction in 1937 and was commissioned in April 1941.
A second battleship, Iowa, started construction at Brooklyn Navy Yard in 1939 and was completed in 1942.
 The third battleship to be constructed at Brooklyn Navy Yard was Missouri, which was launched in 1944 and was the site of the surrender of Japan on September 2, 1945.
After the completion of the battleships, two aircraft carrier orders were placed: one for USS Bennington, laid down in December 1942, and one for USS Franklin D. Roosevelt, laid in 1944.
According to the National Park Service, the Brooklyn Navy Yard eventually constructed "three battleships, two floating workshops, eight tank landing ships, and countless barges and lighters".
The yard also outfitted 250 ships for battle, as well as made repairs to 5,000 ships.

To accommodate the construction of the battleships, dry docks 5 and 6 were constructed.
The Navy re-acquired 25 acres (10 ha) of land, which had been sold to New York City in the 1890s to create Wallabout Market.
The original plans were to build the dry docks in Bayonne, New Jersey, but that location was unsuitable due to its proximity to a munitions arsenal, and the dry docks at Brooklyn Navy Yard were approved in 1941.
The docks would be 1,500 feet (460 m) long by 200 ft (61 m) wide and 60 ft (18 m) deep; at the time, there were no battleships that large.
The docks were ultimately built at a length of 1,067 ft (325 m), which still made them longer than any of the other dry docks.
Construction contracts were awarded in 1941.
Several structures were demolished, including the market and the Cob Dock.
Additionally, a branch of Wallabout Basin that led to the market was filled in, and about 2.3 million cubic yards (1,800,000 m³) of silt was dredged from the basin.
The neighboring Kent Avenue basin on the east side of the site was also filled in.
Afterward, 13,000 piles were driven into the sandy bottom of the basin, and two hundred concrete forms were poured at a rate of 350 cubic yards (270 m³) per hour.
Dry Dock 5 was completed by 1942.
The work also entailed the construction of piers J and K, as well as a 350-short-ton (310-long-ton) hammerhead crane at Pier G, added in 1943.

The Brooklyn Navy Yard was employing 18,000 workers in December 1941, just after the attack on Pearl Harbor.
Following Pearl Harbor, the U.S. officially entered World War II and the number of employees at Brooklyn Navy Yard increased.
By June 1942, more than 42,000 workers were employed.
The Brooklyn Navy Yard started 24/7 operations, and three shifts of eight hours were implemented.
In addition to shipbuilding, workers at the yard created uniforms and flags, as well as packaged food and combat provisions for sailors and soldiers.
During the peak
In preparation for World War II, the Brooklyn Navy Yard was extensively reconstructed. The Navy Yard was expanded slightly to the west by 1.5 acres (0.61 ha), bringing its total area to 356 acres (144 ha), and parts of the mid-19th-century street grid were eliminated in favor of new developments. These structures included the construction of an 800-by-100-foot (244 by 30 m), single-story turret-and-erection shop; the expansion of the Connecticut building ways; and lengthening of Dry Dock 4. By 1939, the yard contained more than five miles (8.0 km) of paved streets, four drydocks ranging in length from 326 to 700 ft (99 to 213 m), two steel shipways, and six pontoons and cylindrical floats for salvage work, barracks for marines, a power plant, a large radio station, and a railroad spur, as well as foundries, machine shops, and warehouses. The new construction involved extensive landfilling operations, some of which yielded artifacts that were centuries old. In one instance, a Civil War-era prison brig was found eight feet underground, while in another, workers unearthed a skeleton thought to be from one of the prison ship martyrs.
The naval shipyards in Brooklyn and Philadelphia were designated for the construction of battleships. The first World War II-era battleship built at Brooklyn Navy Yard was North Carolina, which started construction in 1937 and was commissioned in April 1941. A second battleship, Iowa, started construction at Brooklyn Navy Yard in 1939 and was completed in 1942.  The third battleship to be constructed at Brooklyn Navy Yard was Missouri, which was launched in 1944 and was the site of the surrender of Japan on September 2, 1945. After the completion of the battleships, two aircraft carrier orders were placed: one for USS Bennington, laid down in December 1942, and one for USS Franklin D. Roosevelt, laid in 1944. According to the National Park Service, the Brooklyn Navy Yard eventually constructed "three battleships, two floating workshops, eight tank landing ships, and countless barges and lighters". The yard also outfitted 250 ships for battle, as well as made repairs to 5,000 ships.
To accommodate the construction of the battleships, dry docks 5 and 6 were constructed. The Navy re-acquired 25 acres (10 ha) of land, which had been sold to New York City in the 1890s to create Wallabout Market. The original plans were to build the dry docks in Bayonne, New Jersey, but that location was unsuitable due to its proximity to a munitions arsenal, and the dry docks at Brooklyn Navy Yard were approved in 1941. The docks would be 1,500 feet (460 m) long by 200 ft (61 m) wide and 60 ft (18 m) deep; at the time, there were no battleships that large. The docks were ultimately built at a length of 1,067 ft (325 m), which still made them longer than any of the other dry docks. Construction contracts were awarded in 1941. Several structures were demolished, including the market and the Cob Dock. Additionally, a branch of Wallabout Basin that led to the market was filled in, and about 2.3 million cubic yards (1,800,000 m³) of silt was dredged from the basin. The neighboring Kent Avenue basin on the east side of the site was also filled in. Afterward, 13,000 piles were driven into the sandy bottom of the basin, and two hundred concrete forms were poured at a rate of 350 cubic yards (270 m³) per hour. Dry Dock 5 was completed by 1942. The work also entailed the construction of piers J and K, as well as a 350-short-ton (310-long-ton) hammerhead crane at Pier G, added in 1943.
The Brooklyn Navy Yard was employing 18,000 workers in December 1941, just after the attack on Pearl Harbor. Following Pearl Harbor, the U.S. officially entered World War II and the number of employees at Brooklyn Navy Yard increased. By June 1942, more than 42,000 workers were employed. The Brooklyn Navy Yard started 24/7 operations, and three shifts of eight hours were implemented. In addition to shipbuilding, workers at the yard created uniforms and flags, as well as packaged food and combat provisions for sailors and soldiers. During the peak
Brooklyn Navy Yard