Build after the London Naval Treaty, this class of light cruiser was far more closely related to a very large destroyer than a light cruiser. Although the US were, at the time of their construction, not yet inflicted in any kind of war, the ships were already designed with a look at the increasing Japanese and German air strength, and the increasing dimensions of their destroyers.  

    The theory of battle within the Navy (at least within the Navy's Design Bureau) was still toward the use of battleships, cruisers, and destroyers in large scale surface combat. Thus, the Atlantas were designed to provide flak cover for the fleet during its approach, and during battle, they were to take the lead of destroyer flotillas countering Japanese destroyers.  
In accord with their rôle, the class was fitted with a terrific battery of 127mm dual-purpose guns in twin turrets. Clearly showing their mission and relation to destroyers is their torpedo armament, making them the US Navy's only torpedo-carrying cruiser class in WW2. 
 
    Also showing her decendancy from large destroyers is the interesting fact that Atlanta was the only cruiser class that carried an active SONAR, or close relative of it (whether it was an actual ASDIC or not I don't know, but then I don't know about any other sound-detection devices).  

    In any event, the war showed that the Atlanta class was of a useful design, and accordingly, the Navy projected further ships of the same type, with certain modifications, and gave the name Oakland to the lead ship of that "class". 
Most of the modifications were a simple use of modern technology: modern radar devices were installed, and 40mm guns with radar direction instead of the 28mm manually aimed guns. Also, the Oaklands never had the two flanking turrets, saving considerable topweight.  

    These modifications were also affected on the two surviving Atlanta class ships, San Diego and San Juan.  
However, while the four original vessels excelled in the AA role during the two carrier battles near Guadalcanal, their usefullness in a surface engagement was in question after the fateful Battle of Friday the 13th, also known as First Battle of Guadalcanal. In its course, Atlanta class Light Cruisers Atlanta and Juneau suffered critical hits, which caused the abandonment of Atlanta. Juneau was sunk, with horrendous casualties, on the return cruise to Espiritou Santo, by submarine torpedoes.  

     As last modification applied to these vessels during the war, the first batch of the Oakland class had its torpedos removed in 1945. Thanks to the advanced proximity fuses of the VT type, supersecret and rather effective, these small ships carried a powerful AA battery, which gave to the US carriers well needed and successful air defense.