The CA24 Pensacola and CA25 Salt Lake City are part of the first class of USN "treaty cruisers" and commissioned early 1928; mainly distinguishable by the triple 8" superfiring over the duals, and the flushdeck hull.
http://en.wikipedia.org/wiki/Pensacola_class_cruiser
http://en.wikipedia.org/wiki/USS_Pensacola_(CA-24)
http://en.wikipedia.org/wiki/USS_Salt_Lake_City_(CA-25)