See? It really is called Battery DeRussy! From that sign that you can't quite make out:

HARBOR DEFENSE REGIMENTAL DISTINCTIVE INSIGNIA
Harbor defense regiments were formed in the Coast Artillery Corps from sep companies in 1924. The distinctive insignia of these regiments and station of the regimental headquarters in 1939 are shown on the signs on this battery.
The regiments were broken up in 1944 but the 1st through 7th and 59th exist today as air defense artillery regiments.
This is a typical seacoast gun battery of the period 1892 to 1944.