The Pittsburgh is the first of the second set of Baltimore-class heavy cruisers, laid down in 1943, launched early 1944 and commissioned later that year. Much of the class didn't change in appearance until the end of the war, VJ Day.
Later Baltimore CAs can be identified with single aircraft handling crane along the centerline, with dual 40mm Bofors tub abreast it (the rounded transom hidden under these).
http://en.wikipedia.org/wiki/USS_Pittsburgh_(CA-72)http://en.wikipedia.org/wiki/Baltimore_class_cruiser