The ships had a variety of anti-aircraft weapons, and the weapons mounted changed over time.
Initially, the ships were designed to mount twelve .50 in (12.7 mm) and twelve 1.1 in (27.9 mm) machine guns.
By March 1942, when South Dakota was completed, the anti-aircraft battery was modified to eight .50 in (12.7 mm) and twenty-eight 1.1 in (27.9 mm) machine guns and sixteen 20mm Oerlikon autocannon.
In September of that year, the .50 in (12.7 mm) guns were removed and the number of 1.1 in (27.9 mm) guns reduced to 20.
In their place, the 20mm guns were increased to 16 weapons, and 16 Bofors 40mm guns were added, in four quadruple mounts.

In February 1943, the 1.1 in (27.9 mm) guns and one 20mm gun were replaced with an additional 52 40mm guns, for a total of 68.
In December 1944, the battery was again upgraded, with 72 20mm and 72 Bofors.
In March 1945, the battery was modified for the last time: five 20mm were added and four 40mm removed.
This provided the maximum number of anti-aircraft guns, at 145 guns.
The other three ships followed a similar pattern of upgrades to the anti-aircraft armament.
The ships had a variety of anti-aircraft weapons, and the weapons mounted changed over time. Initially, the ships were designed to mount twelve .50 in (12.7 mm) and twelve 1.1 in (27.9 mm) machine guns. By March 1942, when South Dakota was completed, the anti-aircraft battery was modified to eight .50 in (12.7 mm) and twenty-eight 1.1 in (27.9 mm) machine guns and sixteen 20mm Oerlikon autocannon. In September of that year, the .50 in (12.7 mm) guns were removed and the number of 1.1 in (27.9 mm) guns reduced to 20. In their place, the 20mm guns were increased to 16 weapons, and 16 Bofors 40mm guns were added, in four quadruple mounts.
In February 1943, the 1.1 in (27.9 mm) guns and one 20mm gun were replaced with an additional 52 40mm guns, for a total of 68. In December 1944, the battery was again upgraded, with 72 20mm and 72 Bofors. In March 1945, the battery was modified for the last time: five 20mm were added and four 40mm removed. This provided the maximum number of anti-aircraft guns, at 145 guns. The other three ships followed a similar pattern of upgrades to the anti-aircraft armament.
South Dakota-class battleship (1939)