Omaha class
USS Richomnd, scanned from Terzibaschitsch, Kreuzer der US Navy
    The earliest class of cruiser still in service with the Navy in 1941, the Omaha class was a post-WW1 design. Build to be the eyes of a fleet of battleships, they featured a high speed for cooperation with destroyers, and 152mm guns to fend of any destroyers the enemy might launch against them.

    With four smokestacks, the Omahas looked remarkably like the old four-stacker destroyers which they were to lead.  
Their armament showed the slow change from casemate-mounted weapons to turret-mounted guns. They held a full twelve 152mm guns, of which four were mounted in two twin turrets, one each firing fore and aft, and eight in casemates.  
The casemates were placed in the superstructure, not in the hull, as they had been on most previous classes, and were distributed with four guns firing forward and four firing aft. All casemates were also able to fire to the sides.  
Due to the large topweight lasting on these ships, only multiplied by the high-mounted catapults, the Navy removed two of the aft firing casemate-mounted guns in 1939.

    The vessels were the fastest U.S. cruisers at the time of their commision.

    None of these units saw active fleet duty which could be compared to the kind of duty the other cruisers had. Marblehead and Raleigh saw battle, the former in the ABDA forces in 1942, the latter in the 1943 Battle of Kommandorski Islands, in the Aleutians. Raleigh and Detroit were in Pearl Harbor at the time of the attack, and Raleigh suffered a critical torpedo hit.
    Several ships of this class saw service in the North Pacific ToO, including Raleigh, Richmond and Concord 
All ships were serving in the Atlantic at least once during the war, however.  

Armament (Guns)
10 x 152mm L/53 as detailed above   
8 x 76mm L/50    
12 x 28mm   
8 x 20mm
Armament (Torpedoes)
6 x 533mm TT
Standard: 7000 tons  
          Full: 9150 tons   
Length: 167.8 meters   
Beam: 16.9 meters   
Draught: 6.1 meters   
Height (Mast): 33.5 meters   
Crew: 458 peace   
Speed: 34 knots
Complement (Planes)
Two floatplanes
Ships in class: 
CL-4 Omaha  
CL-5 Milwaukee  
CL-6 Cincinnati   
CL-7 Raleigh  
CL-8 Detroit
CL-9 Richmond  
CL-10 Concord  
CL-11 Trenton  
CL-12 Marblehead  
CL-13 Memphis